Multicolor image-forming material and method for forming multicolor image

ABSTRACT

A multicolor image-forming material which comprises an image-receiving sheet comprising a support having thereon a coating layer including at least an image-receiving layer, and a plurality of heat transfer sheets each comprising a support having coating layers including at least a light-to-heat converting layer and an image-forming layer, wherein the ratio of the optical density (OD) of the image-forming layer in each heat transfer sheet to the layer thickness, OD/layer thickness (μm unit), is 1.50 or more, the recording area of a multicolor image of the heat transfer sheet is 515 mm or more multiplying 728 mm or more, the definition of a transferred image is 2,400 dpi or more, the coating layer in the image-receiving sheet and/or the coating layers in each heat transfer sheet has at least one layer containing a dispersant and a matting layer having an average particle size of from 0.05 to 50 pm, and the coating layer further contains, if necessary, prescribed specific spherical fine particles and/or a prescribed specific spherical acryl-based polymer.

FIELD OF THE INVENTION

[0001] The present invention relates to a multicolor image-formingmaterial for forming a full color image of high definition with a laserbeam, and a method for forming a multicolor image. In particular, thepresent invention relates to a multicolor image-forming material whichis useful for forming a color proof (DDCP: direct digital color proof)or a mask image from digital image signals by laser recording in thefield of printing, and a method for forming a multicolor image.

BACKGROUND OF THE INVENTION

[0002] In the field of graphic arts, printing of a printing plate isperformed with a set of color separation films formed from a colororiginal by a lith film. In general, color proofs are formed from colorseparation films before actual printing work for checking an error inthe color separation step and the necessity for color correction. Colorproofs are desired to realize high definition which makes it possible tosurely reproduce a half tone image and have performances such as highstability of processing. Further, for obtaining color proofs closelyapproximating to an actual printed matter, it is preferred to usematerials which are used in actual printing as the materials for makingcolor proofs, e.g., the actual printing paper as the base material andpigments as the coloring materials. As the method for forming a colorproof, a dry method not using a developing solution is strongly desired.

[0003] As the dry method for forming color proofs, a recording system ofdirectly forming color proofs from digital signals has been developedwith the spread of electronized system in preprocessing of printing(pre-press field) in recent years. Such electronized system aims atforming in particular high image quality color proofs, generallyreproduces a dot image of 150 lines/inch or higher. For recording aproof of high image quality from digital signals, laser beams capable ofmodulation by digital signals and capable of finely diaphragmingrecording light are used as recording heads. Therefore, the developmentof an image-forming material having high recording sensitivity to laserbeams and exhibiting high definition property capable of reproducinghighly minute dots is required.

[0004] As the image-forming material for use in a transfer image-formingmethod using laser beams, a heat fusion transfer sheet comprising in theorder of a support having a light-to-heat converting layer which absorbslaser beams and generates heat, and an image-forming layer whichcontains a pigment dispersed in components such as a heat fusion typewax and a binder is known (JP-A-5-58045 (the term “JP-A” as used hereinmeans an “unexamined published Japanese patent application”)). In theimage-forming method using such an image-forming material, animage-forming layer corresponding to the area of a light-to-heatconverting layer irradiated with laser beams is fused by heat generatedin that area and transferred onto an image-receiving sheet arranged onthe transfer sheet by lamination, thus a transferred image is formed onthe image-receiving sheet.

[0005] Further, a heat transfer sheet comprising a support havingprovided thereon a light-to-heat converting layer containing alight-to-heat converting material, an extremely thin heat-peeling layer(from 0.03 to 0.3 μm), and an image-forming layer containing a coloringmaterial in this order is disclosed in JP-A-6-219052. In this heattransfer sheet, the bonding strength between the image-forming layer andthe light-to-heat converting layer bonded through the interveningheat-peeling layer is reduced by laser beam irradiation, as a result, ahighly minute image is formed on an image-receiving sheet arranged onthe heat transfer sheet by lamination. The image-forming method by theheat transfer sheet utilizes so-called ablation, specifically theheat-peeling layer partially decomposes at the area irradiated withlaser beams and vaporizes, thereby the bonding strength of theimage-forming layer and the light-to-heat converting layer at that areais reduced and the image-forming layer at that area is transferred tothe image-receiving sheet laminated thereon.

[0006] These image-forming methods have various advantages that anactual printing paper provided with an image-receiving layer (anadhesion layer) can be used as the material of an image-receiving sheet,and a multicolor image can be easily obtained by transferring imagesdifferent in colors in sequence on the image-receiving sheet. Inparticular, the image-forming method utilizing ablation has theadvantage that highly minute image can be easily obtained, and so thesemethods are useful for forming a color proof (DDCP: direct digital colorproof) or a highly minute mask image.

[0007] DTP is prevailing more and more and the intermediate processusing films is omitted when CTP (computer to plate) is used, and theneed for proof is shifting from analog proof to DDCP. In recent yearsthe demand for large sized high grade DDCP highly stable and excellentin coincidence in printing has increased.

[0008] High definition printing can be effected according to a heattransfer method by laser irradiation, and as the laser heat transfermethods, (1) a laser sublimation method, (2) a laser ablation method,and (3) a laser fusion method are conventionally used, but any of thesemethods has a drawback such that the shape of a recorded dots are notsharp. In (1) a laser sublimation method, since dyes are used as thecoloring material, the approximation of proofs to printed matters is notsufficient, further, since this is a method of sublimating coloringmaterials, the outline of a dot is fuzzy, and so definition is notsufficiently high. On the other hand, since pigments are used as thecoloring materials in (2) a laser ablation method, the approximation toprinted matters is good, but since this is a method of sputteringcoloring materials, the outline of a dot is also fuzzy as in thesublimation method, and so definition is not sufficiently high. Further,in (3) a laser fusion method, a molten substance flows, and so theoutline of a dot is not also clear.

[0009] Moreover, these image-forming materials comprising a heattransfer sheet and an image-receiving sheet contain a matting agent inthe constituting layers to improve the quality of the image to beobtained, but there is such a problem that the contact of the heattransfer sheet and the image-receiving sheet becomes insufficientpartially at recording time due to the cohesion of the matting agent,which hinders transferring and causes so-called spot-like image blankareas (i.e., clear spots). Further, the pot life of a coating solutioncontaining a matting agent is relatively short and inconvenient.

SUMMARY OF THE INVENTION

[0010] Accordingly, the object of the present invention is to solve theabove-described problems of the prior art technique and to accomplishthe following objects. That is, an object of the present invention is toprovide a large sized high grade DDCP which has high quality and ishighly stable and excellent in coincidence in printing. Specifically,the present invention is characterized in that: 1) a heat transfer sheetcan provide excellent sharpness of dots and stability by transfer of amembrane of coloring material, which is not influenced by light sourcesof illumination as compared with the pigment material and the printedmatter, 2) an image-receiving sheet can receive stably and surely theimage-forming layer in a heat transfer sheet by laser energy, 3)transfer to actual printing paper can be effected corresponding to therange of at least from 64 to 157 g/m² such as art paper (coat paper),mat paper and finely coated paper, delicate texture can be imaged, and ahigh-key part can be reproduced accurately, and 4) extremely stabletransfer pealing property can be obtained.

[0011] A further object of the present invention is to provide a methodfor forming a multicolor image which can form an image having good imagequality and stable transfer image density on an image-receiving sheeteven when recording is performed by multi-beam laser beams of highenergy under different temperature and humidity conditions.

[0012] Still further object of the present invention is to provide animage-forming material capable of using a coating solution having a longpot life and not accompanied by the blank area (i.e., the clear spot) ofan image resulting from a matting agent, and a producing method of sucha material.

[0013] That is, the present invention has been attained by the followingmeans.

[0014] (1) A multicolor image-forming material which comprises animage-receiving sheet comprising a support having thereon a coatinglayer including at least an image-receiving layer, and a plurality ofheat transfer sheets each comprising a support having coating layersincluding at least a light-to-heat converting layer and an image-forminglayer, wherein the ratio of the optical density (OD) of theimage-forming layer in eachheat transfer sheet to the layer thickness,OD/layer thickness (μunit), is 1.50 or more, the recording area of amulticolor image of the heat transfer sheet is a size of 515 mm or moremultiplying 728 mm or more, the definition of a transferred image is2,400 dpi or more, and the coating layer in the image-receiving sheetand/or the coating layers in each heat transfer sheet has at least onelayer containing a dispersant and a matting agent having an averageparticle size of from 0.05 to 50 μm.

[0015] (2) The multicolor image-forming material as described in theabove item (1), wherein the dispersant is a surfactant and/or a polymer.

[0016] (3) The multicolor image-forming material as described in theabove item (1) or (2), wherein the average particle size of the mattingagent is from 0.1 to 30 μm.

[0017] (4) A method for manufacturing the multicolor image-formingmaterial as described in the above item (1), (2) or (3) which comprisesthe steps of dispersing the matting agent in a dispersion medium withthe dispersant in advance to prepare a coating solution containing thedispersed matting agent, coating and drying the prepared coatingsolution to form the layer containing the matting agent, to therebyobtain the multicolor image-forming material.

[0018] (5) The method for manufacturing the multicolor image-formingmaterial as described in the above item (4), wherein the water contentin the dispersion medium at dispersing the matting agent is 50% or less.

[0019] (6) The multicolor image-forming material as described in theabove item (1), wherein any coating layer in the heat transfer sheetand/or the image-receiving sheet contains spherical fine particleshaving an average particle size of from 0.10 to 3.0 μm and a particlesize distribution (L₂₅/L₇₅) of 2.0 or less.

[0020] (7) The multicolor image-forming material as described in theabove item (6), wherein the spherical fine particles are amorphous fineparticles.

[0021] (8) The multicolor image-forming material as described in theabove item (6) or (7), wherein the spherical fine particles have anaverage particle size of from 1.1 to 3.0 μm.

[0022] (9) The multicolor image-forming material as described in theabove item (6), (7) or (8), wherein the spherical fine particles have aspecific gravity of from 1.1 to 3.5 at 25° C.

[0023] (10) The multicolor image-forming material as described in theabove item (6), (7), (8) or (9), wherein the spherical fine particleshave a specific gravity of from 1.1 to 1.4 at 25° C.

[0024] (11) The multicolor image-forming material as described in theabove item (1) or (16), wherein any coating layer in either the heattransfer sheet or the image-receiving sheet contains an acryl-basedpolymer having a glass transition point of from 10 to 120° C.

[0025] (12) The multicolor image-forming material as described in theabove item (11), wherein the light-to-heat converting layer in the heattransfer sheet contains an acryl-based polymer having a glass transitionpoint of from 10 to 120° C.

[0026] (13) The multicolor image-forming material as described in theabove item (11) or (12), wherein the acid value of the acryl-basedpolymer is 300 or less.

[0027] (14) The multicolor image-forming material as described in theabove item (11), (12) or (13), wherein the acryl-based polymer hasstructure containing a styrene derivative moiety in the polymermolecule.

[0028] (15) The multicolor image-forming material as described in any ofthe above items (1) to (14), wherein the definition of a transferredimage is 2,600 dpi or more.

[0029] (16) The multicolor image-forming material as described in any ofthe above items (1) to (15), wherein the ratio of the optical density(OD) of the image-forming layer in each heat transfer sheet to the layerthickness, OD/layer thickness (μm unit), is 1.80 or more.

[0030] (17) The multicolor image-forming material as described in any ofthe above items (1) to (16), wherein the recording area of a multicolorimage is 594 mm multiplying 841 mm or more.

[0031] (18) The multicolor image-forming material as described in any ofthe above items (1) to (17), wherein the contact angle of theimage-forming layer in each heat transfer sheet and the image-receivinglayer in the image-receiving sheet with water is from 7.0 to 120.0°.

[0032] (19) The multicolor image-forming material as described in any ofthe above items (1) to (18), wherein the ratio of the optical density(OD) of the image-forming layer in each heat transfer sheet to the layerthickness, OD/layer thickness (μm unit), is 1.80 or more, and thecontact angle of the image-receiving sheet with water is 89° or less.

[0033] (20) The multicolor image-forming material as described in any ofthe above items (1) to (18), wherein the ratio of the optical density(OD) of the image-forming layer in each heat transfer sheet to the layerthickness, OD/layer thickness (μm unit), is 2.50 or more.

[0034] (21) A method for forming a multicolor image using theimage-receiving sheet as described in any of the above items (1) to (20)and four or more heat transfer sheets as described in any of the aboveitems (1) to (20) comprising the steps of superposing the image-forminglayer in each heat transfer sheet and the image-receiving layer in theimage-receiving sheet vis-a-vis, and irradiating the heat transfer sheetfrom the support side with laser beams and transferring the area of theimage-forming layer subjected to laser beam irradiation onto theimage-receiving layer in the image-receiving sheet, to thereby effectimage-recording, wherein the image-forming layer in the laser beamirradiation area is transferred to the image-receiving sheet in amembrane state.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035]FIG. 1 is a drawing showing the outline of the scheme ofmulticolor image-forming by membrane heat transfer (i.e., thin film heattransfer) by irradiation with a laser.

[0036]FIG. 2 is a drawing showing an example of constitution of arecording unit for laser heat transfer.

[0037]FIG. 3 is a drawing showing an example of constitution a heattransfer unit.

[0038]FIG. 4 is a drawing showing the scheme of a system using arecording unit FINALPROOF for laser heat transfer.

DESCRIPTION OF REFERENCE CHARACTERS:

[0039]1: Recording unit

[0040]2: Recording head

[0041]3: Subsidiary scanning rail

[0042]4: Recording drum

[0043]5: Heat transfer sheet-loading unit

[0044]6: Image-receiving sheet roll

[0045]7: Carrier roller

[0046]8: Squeeze roller

[0047]9: Cutter

[0048]10: Heat transfer sheet

[0049]10K, 10C, 10M, 107: Heat transfer sheet rolls

[0050]12: Support

[0051]14: Light-to-heat converting layer

[0052]16: Image-forming layer

[0053]20: Image-receiving sheet

[0054]22: Support for image-receiving sheet

[0055]24: Image-receiving layer

[0056]30: Laminate

[0057]31: Discharge-receiving table

[0058]32: Discard port

[0059]33: Discharge port

[0060]34: Air

[0061]35: Discard box

[0062]42: Actual paper

[0063]43: Heat roller

[0064]44: Insert-receiving table

[0065]45: Mark showing the position of placement

[0066]46: Insert roller

[0067]47: Guide made of heat resisting sheet

[0068]48: Peeling claw

[0069]49: Guide plate

[0070]50: Discharge port

DETAILED DESCRIPTION OF THE INVENTION

[0071] As a result of eager investigation to provide a B2/A2 to Bl/Al orlarger sized high grade DDCP which is highly stable and excellent incoincidence in printing, the present inventors have developed a heattransfer recording system by laser irradiation for DDCP which comprisesan image-forming material of a B2 or larger size having performances oftransfer to actual printing paper, reproduction of actual dots and of apigment type, output driver, and high grade CMS software.

[0072] The characteristics of the heat transfer recording system bylaser irradiation which has been developed by the present inventors, theconstitution of the system and the outline of technical points are asfollows. As the characteristics of performances, (1) since the dotshapes are sharp, dots which are excellent in approximation to theprinted matter can be reproduced, (2) the approximation of hue to theprinted matter is good, and (3) since the recorded quality is hardlyinfluenced by the surrounding temperature and humidity and repeatingreproducibility is good, a stable proof can be formed. The technicalpoints of the material capable of obtaining such characteristics ofperformances are the establishment of the technique of membrane transfer(i.e., thin film transfer), and the improvement of the retentivity ofvacuum adhesion of the material required of a laser heat transfersystem, following up of high definition recording, and the improvementof heat resistance. Specifically, (1) thinning of a light-to-heatconverting layer by the introduction of an infrared absorbing dye, (2)strengthening of the heat resistance of a light-to-heat converting layerby the introduction of a polymer having a high Tg, (3) stabilization ofhue by the introduction of a heat resisting pigment, (4) control of theadhesive strength and the cohesive strength of the material by theaddition of low molecular weight components, such as a wax and aninorganic pigment, and (5) the provision of vacuum adhesion property tothe material not being accompanied by the deterioration of an imagequality by the addition of a matting agent to a light-to-heat convertinglayer, can be exemplified. As the technical points of the system, (1)carrying by air for continuous accumulation of multi sheets of films ina recording unit, (2) insert of a heat transfer unit on an actual paperfor reducing curling after transfer, and (3) connection of output driverof a wide use having system connecting expendability, can beexemplified. The laser irradiation heat transfer recording systemdeveloped by the present inventors consists of diverse characteristicsof performances, system constitution and technical points as describedabove, but these are exemplifications and the present invention is notlimited thereto.

[0073] The present inventors have performed development on the basis ofthoughts that individual material, each coating layer such as alight-to-heat converting layer, a heat transfer layer and animage-receiving layer, and each heat transfer sheet and image-receivingsheet are not present individually separately but they must functionorganically and synthetically, further these image-forming materialsexhibit the highest possible performances when combined with a recordingunit and a heat transfer unit. The present inventors have sufficientlyexamined each coating layer and the constituting materials of animage-forming material and prepared each coating solution bringing outthe best of their characteristics to make the image-forming material,and found proper ranges of various physical properties so that theimage-forming material can exhibit the best performance. As a result,the relationships between each material, each coating layer and eachsheet with the physical properties have been investigated thoroughly,and by functioning them organically and synthetically with the recordingunit and the heat transfer unit, a high performance image-formingmaterial could be found unexpectedly. The present invention is importantsince the positioning of the present invention is directly related tothe system developed by the present inventors as the introduction of amatting agent to coating layers such as a light-to-heat convertinglayer, an image-forming layer, an image-receiving layer and a backinglayer. The present invention applies a matting agent to theimage-forming material having the ratio of the optical density (OD) ofthe image-forming layer in each heat transfer sheet to the layerthickness, OD/layer thickness (μunit), of 1.50 or more, the recordingarea of a multicolor image of each heat transfer sheet of a size of 515mm or more multiplying 728 mm or more, and the definition of atransferred image of 2,400 dpi or more.

[0074] The multicolor image-forming material according to the presentinvention (hereinafter also simply referred to as an image-formingmaterial) comprises an image-receiving sheet and a plurality of heattransfer sheets. One or more matting agent-containing layers areprovided in the coating layers in the image-receiving sheet and/or eachheat transfer sheet.

[0075] In the present invention, the ratio of the optical density (OD)of the image-forming layer to the layer thickness, OD/layer thickness(μm unit), is the ratio of the optical density of the image-forminglayer to the layer thickness of the image-forming layer measured in μmunit. The optical density is the reflection optical density obtained bytransferring the image having been transferred from a heat transfersheet to an image-receiving sheet further to Tokuryo art paper, andmeasuring by color mode of each color such as yellow (Y), magenta (M),cyan (C) or black (K) with a densitometer (X-rite 938, manufactured byX-rite Co.). The layer thickness of the image-forming layer is measuredby observing the cross section of the heat transfer sheet beforeimage-recording with a scanning electron microscope. In the presentinvention, an image having high optical density and good definition canbe obtained by making OD/layer thickness (μm unit) 1.5 or more. When theOD/layer thickness is less than 1.5, sufficient optical density cannotbe obtained or definition lowers, a good image cannot be obtained ineither case.

[0076] The present invention also concerns the multicolor image-formingmaterial in which the recording area of a multicolor image of each heattransfer sheet is a large size of 515 mm or more multiplying 728 mm ormore, and the definition of a transferred image is high definition of2,400 dpi or more.

[0077] In the present invention as described above, one or more layerscontaining a matting agent having an average particle size of from 0.05to 50 μm are provided in the coating layers in the image-receiving sheetand/or each heat transfer sheet. The layers containing a matting agentand the forming method of the layers are described below.

[0078] (1) Matting agent

[0079] In the present invention, the matting agent comprises solidparticle and used to make the surface of the image-receiving sheet orthe heat transfer sheet uneven. Here, pigments which are mainly used fordisplaying images are excluded from the solid particles. The mattingagent is preferably substantially colorless.

[0080] The matting agents for use in the present invention are notparticularly limited as to the material and the shape so long as theyhave an average particle size of from 0.05 to 50 μm. As the material,inorganic and organic fine particles can be exemplified. The examples ofthe inorganic fine particles include metal salts, e.g., silica, titaniumoxide, aluminum oxide, zinc oxide, magnesium oxide, barium sulfate,magnesium sulfate, aluminum hydroxide, magnesium hydroxide and boronnitride, kaolin, clay, talc, zinc flower, lead white, zeeklite, quartz,diatomaceous earth, pearlite, bentonite, mica, and synthetic mica. Theexamples of the organic fine particles include olefin resins, e.g.,polystyrene and polyethylene, acryl resin particles, e.g., fluorineresin particles, guanamine resin particles, and polymethyl methacrylate,styrene-acryl copolymer resin particles, silicone resin particles,melamine resin particles and epoxy resin particles. Of these fineparticles, in the case of polymer matting agents, so-called threedimensional network structure by crosslinking for preventing dissolutiondue to the solvent in a coating solution is also preferably used. Of theabove compounds, matting agents of inorganic compounds are particularlypreferred, because swelling and subsequent deformation due to thesolvent in a coating solution is difficult to occur.

[0081] The shape of the matting agent is not especially restricted andspherical, irregular and cubic shapes can be used.

[0082] The matting agents for use in the present invention generallyhave an average particle size of from 0.05 to 50 μm, preferably from 0.1to 30 μm, and more preferably from 0.3 to 15 μm. The average particlesize of the matting agent can be obtained, e.g., by photographing theparticles with a scanning electron microscope.

[0083] The addition amount of the matting agent is generally from 0.1 to100 μg/m², preferably from 1 to 70 mg/m².

[0084] (2) Layer Containing Matting Agent

[0085] The coating layer of the heat transfer sheet of the presentinvention comprises at least a light-to-heat converting layer and animage-forming layer on a support but, if necessary, a peeling layer andan image-protective layer may be provided besides these layers. Thematting agent of the present invention may be added to any of theselayers but the matting agent is particularly preferably added to alight-to-heat converting layer.

[0086] The coating layer of the image-receiving sheet of the presentinvention comprises at least an image-receiving layer on a support but,if necessary, a cushioning layer may be provided. The matting agent ofthe present invention may be added to any of these layers, but thematting agent is particularly preferably added to a cushioning layer.

[0087] The thickness, binder and other additives of the layerscontaining the matting agent are not particularly restricted. Forexample, the thickness is preferably from 0.05 to 40 μm, preferably from0.1 to 30 μm. As the binders, a polyurethane resin, an epoxy resin,apolyvinyl butyral resin, a vinyl acetate resin, polyvinyl chlorideacetate resin can be exemplified.

[0088] (3) Dispersion Method of Matting Agent and Dispersant

[0089] A matting agent-containing layer is formed by coating a coatingsolution containing a matting agent and drying. At this time, it ispreferred that a matting agent is dispersed in advance in the presenceof a dispersant. The terminology “dispersion” used herein means thestate that the matting agent is not cohered to each other and uniformlysuspended in a dispersion medium as a liquid. With respect todispersion, e.g., Takao Karikomi, Masumi Koishi and Tohru Hidakacompiled, Nyuka-Bunsan Gijutsu Ohyo Handbook (Handbook of TechnicalApplications of Emulsification and Dispersion), Science Forum Co., Ltd.(1987), and Toshio Kajiuchi and Hiroki Usui compiled, Bunsan-keiRheology to Bunsanka Gijutsu (Rheology of Dispersion System andTechniques of Dispersion), Shinzan-Sha Publishing Co., Ltd. (1991) canbe referred to.

[0090] As the method of dispersing a matting agent in a dispersionmedium, generally a method of mixing a matting agent with a dispersantand applying external force, e.g., shearing force, but in the presentinvention, a dispersant is further added to a matting agent and adispersion medium. A dispersion method is not particularly limited and aball mill and a paint shaker are used. With respect to dispersion, theabove Nyuka-Bunsan Gijutsu Ohyo Handbook, p. 466 and the aboveBunsan-kei Rheology to Bunsanka Gijutsu, p. 357 can be referred to.

[0091] Well-known dispersants can be used in the present invention. Thespecific examples of dispersants include surfactants and polymersincluding oligomers. The examples of surfactants include anionicsurfactants, e.g., sodium alkylbenzenesulfonates and sodiumalkylsulfates, cationic surfactants, e.g., alkylpyridinium chlorides andalkylpyridinium bromides, and nonionic surfactants, e.g.,polyoxyethylenealkylphenols and polyoxyethylene fatty acid esters. Inaddition, betaine surfactants having both positive and negative electriccharges in the molecule can also be used. Natural products, e.g.,saponin, can also be used as surfactant. Surfactants are described,e.g., in Tokiyuki Yoshida, Shinichi Shindo, Tadayoshi Ohgaki and KiyoshiNakayama compiled, Kaimen Kasseizai Handbook (Handbook of Surfactants),Kogaku Tosho Shuppan Co., Ltd. (1987).

[0092] The examples of the polymers include polyvinyl alcohol,polyacrylamide, sodium polyacrylate, polyethylene oxide and derivativesof it, polyacrylate and copolymers of it, cellulose and derivatives ofit, starch and derivatives of it, protein and derivatives of it, andnatural polysaccharide and derivatives of it. Since the kind ofpreferred polymer varies according to the kind of the matting agent andthe dispersant, and so cannot be said unconditionally, but when thedispersion medium is water, polyvinyl alcohol, cellulose and derivativesof it are preferably used, and when the dispersion medium is an organicsolvent, polyacrylic ester and a copolymer of it, polyethylene oxide andderivatives of it are preferably used. The molecular weight of thepolymers is preferably from 200 to 500,000 or so, more preferably from500 to 100,000 or so.

[0093] (4) Dispersion Medium

[0094] The dispersion medium is not particularly restricted, andwell-known dispersion medium, e.g., methyl ethyl ketone, methyl isobutylketone, ethyl acetate, butyl acetate, methyl alcohol, ethyl alcohol,n-propyl alcohol, i-propyl alcohol and N-methylpyrrolidone can be used.These compounds may be used alone or as mixture. The examples of use asmixture include methyl ethyl ketone/n-propyl alcohol (50/50), methylethyl ketone/n-propyl alcohol (80/20), methyl ethyl ketone/n-propylalcohol (20/80), methyl ethyl ketone/methyl alcohol (50/50), methylethyl ketone/methyl isobutyl ketone (90/10), ethyl acetate/butyl acetate(80/20), ethyl acetate/methyl alcohol (40/60), methyl ethylketone/N-methylpyrrolidone (50/50), methyl ethylketone/N-methylpyrrolidone (80/20), and methyl ethylketone/N-methylpyrrolidone (20/80). The dispersion medium may containwater. As such examples, methyl alcohol/water (90/10) and methyl ethylketone/water (95/5) can be exemplified (the numbers in parentheses meansthe mass (i.e., the weight) of each component). The content of water ina dispersion medium is preferably 50% or less, particularly preferably30% or less.

[0095] (5) Coating method

[0096] The matting agent-containing layer of the present invention maybecoated by well-known methods without limitation. Well-known coaters,e.g., a bar coater, a spin coater, and a slide coater can be used.

[0097] In one embodiment of the image-forming material of the presentinvention, prescribed spherical fine particles are added to any coatinglayer of the heat transfer sheet and/or the image-receiving sheet, andthe spherical fine particles contained in the coating layer areeffective for enhancing vacuum drawing.

[0098] That is, in the image-forming material of the present invention,image-recording is performed by irradiation of laser beams with the heattransfer sheet and the image-receiving sheet being superposed vis-a-vis.If the gap between the heat transfer sheet and the image-receiving sheetis too big at this time, membrane transfer is not effectedsatisfactorily and a good image cannot be obtained. Accordingly, avacuum drawing is generally performed before image formation inimage-recording to heighten the adhesion of the heat transfer sheet andthe image-receiving sheet.

[0099] In one embodiment of the image-forming material of the presentinvention, certain spherical fine particles are added to any coatinglayer of the heat transfer sheet and/or the image-receiving sheet, andthe spherical fine particles contained in the coating layer areextremely effective for enhancing the effect of vacuum drawing. When thespherical fine particles of the present invention are added to thecoating layers and at the same time OD/layer thickness (μunit) is made1.5 or more, a very good image can be obtained. In particular, when animage area is large, the effect of vacuum drawing is liable to lower,the combination of using the spherical fine particles of the presentinvention and making OD/layer thickness (μunit) 1.5 or more is effectivein the case of an image of an area of 515 mm or more multiplying 728 mmor more.

[0100] The spherical fine particles in the present invention aredetermined as follows. A particle is photographed by a scanning electronmicroscope of 10,000 magnifications, the longest particle L1 and L2which is the diameter of a circle having the same area as the particleare measured, and L2/L1 is computed. L2/L1 is computed with one hundredfine particles, and when La, which is the average value of L2/L1, is 0.8or more, the particles are “spherical”. La of the spherical fineparticles for use in one embodiment of the present invention is 0.8 ormore, more preferably 0.85 or more. When fine particles having L2/L1 ofless than 0.8 are used, there arises a problem that the scratch strengthof the multicolor image-forming material of the present invention isdeteriorated.

[0101] The average particle diameter of the spherical fine particlesused in the present invention is the average value Lb of L2 of onehundred fine particles. The average particle diameter of the sphericalfine particles for use in one embodiment of the present invention isfrom 0.10 to 3.0 μm, more preferably from 1.1 to 3.0 μm. When fineparticles having an average particle diameter of less than 0.1 μm areused, the effect of the addition is not sufficient, while when itexceeds 3.0 μm, there arises a problem of the precipitation of the fineparticles in a coating solution.

[0102] The particle size distribution of the spherical fine particles inthe present invention is represented by the ratio of the average of highranking 25 particles L₂₅ of L2 to the average of high ranking 75particles L₇₅, L₂₅/L₇₅, measured with 100 fine particles. L₂₅/L₇₅ of thespherical fine particles for use in one embodiment of the presentinvention is preferably 2.0 or less, more preferably 1.5 or less. WhenL₂₅/L₇₅ exceeds 2, since fine particles having a big particle diameterare present, there arises a problem of the precipitation of the fineparticles in a coating solution similarly to the case where the averagediameter of the fine particles is large.

[0103] As the spherical fine particles, either inorganic or organic fineparticles can be used. The examples of the inorganic fine particlesinclude fine particles of metal salts, e.g., silica, titanium oxide,aluminum oxide, zinc oxide, magnesium oxide, barium sulfate, magnesiumsulfate, aluminum hydroxide, magnesium hydroxide and boron nitride,kaolin, clay, talc, zinc flower, lead white, zeeklite, quartz,diatomaceous earth, pearlite, bentonite and mica. The examples of theorganic fine particles include fine particles of fluorine resin,guanamine resin, acrylate resin, silicone resin, epoxy resin, styreneresin, and copolymers of these resins.

[0104] Of these fine particles, fine particles having a specific gravityof preferably from 1.1 to 3.5, more preferably from 1.1 to 1.4, andamorphous particles are particularly preferably used.

[0105] In one embodiment of the multicolor image-forming material of thepresent invention, these spherical fine particles are added to either orboth coating layer (s) of the heat transfer sheet and/or theimage-receiving sheet in an amount of from 1 to 100 mg/m², morepreferably from 2 to 70 mg/m², per a sheet. When the addition amount islittle, the effect of addition is insufficient, while when the amount istoo much, there arises a drawback that the quality of the image obtainedis deteriorated.

[0106] In one embodiment of the image-forming material of the presentinvention, a definite acryl-based polymer is contained in any coatinglayer in either the heat transfer sheet and/or the image-receivingsheet, and this acryl-based polymer contained in a coating layer has theeffect of improving the definition of a transferred image.

[0107] That is, in the laser heat transfer recording system developed bythe present inventors, the definition of an image is very important forrepresenting characters and fine lines in high quality. When thedefinition of an image is inferior, characters and lines are jagged anddifficult to read or lines are broken halfway. As the means forimproving the definition of a transferred image, e.g., heightening theratio of the pigment to the binder (P/B ratio) in the image-forminglayer, or adjusting the addition amounts of additives in theimage-forming layer, to thereby control the physical properties of theimage-forming layer can be exemplified. However, if P/B ratio isincreased too much, the dispersion stability of the pigment lowers, andin the adjustment of the physical properties of the image-forming layer,other performances are deteriorated in many cases, e.g., transfersensitivity is reduced, thus the adjustment does not go well easily andsuch is the state at present.

[0108] As a result of eager investigation by the present inventors ofthe addition of various additives to the light-to-heat converting layerand the image-receiving layer for improving definition, we have foundthat the effect of improving the definition of a transferred image canbe obtained by adding a small amount of definite acryl-based polymer toeither the light-to-heat converting layer of the heat transfer sheet orthe image-receiving sheet, thus the embodiment of the addition of adefinite acryl-based polymer to the coating layer has been completed.

[0109] The acryl-based polymer for use in one embodiment of the presentinvention preferably has a glass transition point of from 10 to 120° C.,more preferably from 30 to 110° C. When the glass transition point islower than 10° C., the glass transition point of the light-to-heatconverting layer itself easily lowers, which causes the degradation ofthe heat resistance of the light-to-heat converting layer. While whenthe glass transition point is higher than 120° C., transfer sensitivitylowers in some cases.

[0110] The acid value of the acryl-based polymer is preferably 300 orless, more preferably 250 or less. When the acid value of the polymer istoo high, the coating layer is liable to be influenced by thesurrounding temperature and humidity of laser recording.

[0111] When the acryl-based polymer for use in one embodiment of thepresent invention contains a styrene derivative moiety in the polymermolecule, the improving effect of definition is great for the additionamount and, further, in particular the hue of the cyan image preferablyapproximates to the printed matter at laser recording time.Specifically, since the generation of coloring components resulting fromheat decomposition of a light-to-heat converting agent and the migrationof the coloring components to the image-forming layer at laser recordingtime are inhibited, b* in L*a*b* color specification approximates to theprinted matter.

[0112] The content of the styrene derivative in the polymer ispreferably from 1 to 90%, more preferably from 20 to 80%.

[0113] The effect of the addition can be obtained when the acryl-basedpolymer is added to either the light-to-heat converting layer of theheat transfer sheet or added to image-receiving layer of theimage-receiving sheet. However, for obtaining the effect of improvingthe definition to every color, the acryl-based polymer is morepreferably added to the heat transfer sheet.

[0114] When the acryl-based polymer is added to the heat transfer sheet,not only the above-described hue is improved but the dispersionstability of the matting agent, which is added to give a vacuum adhesionproperty, is improved, hence further preferred.

[0115] The addition amount of the acryl-based polymer in the presentinvention varies a little according to the kind of the polymer to beadded, but is preferably from 0.01 to 30 mass % of the entire solidcontent in the layer to be added, more preferably from 0.1 to 20 mass %.

[0116] The molecular weight of the acryl-based polymer is notparticularly limited. Specifically, from oligomers having a weightaverage molecular weight of about 1,500 to polymers having a molecularweight of about 50,000 can be used but those having an extremely lowmolecular weight are liable tobe diffused during storage, hence notpreferred.

[0117] The acryl-based polymermaybe added to the light-to-heatconverting solution separately as the additive, or may be dispersed witha matting agent and added to the light-to-heat converting solution asthe dispersion solution of the matting agent.

[0118] As the specific examples of the acryl-based polymers, astyrene/acrylic acid copolymer, a styrene/methacrylic acid copolymer, astyrene/α-methylstyrene/acrylic acid copolymer, a styrene/butylacrylate/methyl methacrylate copolymer, a styrene/methyl acrylatecopolymer, a styrene/methyl methacrylate copolymer, astyrene/α-methylstyrene/methyl methacrylate copolymer, astyrene/α-methylstyrene/ethyl acrylate copolymer, and a styrene/butylmethacrylate can be exemplified, but the present invention is notlimited thereto.

[0119] In the image-forming material of the present invention, eachcontact angle with water of the image-forming layer in each heattransfer sheet and the image-receiving layer in the image-receivingsheet is preferably from 7.0 to 120.00. The contact angle is a barometerof the compatibility of the image-forming layer with the image-receivinglayer, i.e., transferability, and the contact angle is more preferablyfrom 30.0 to 100.00. Further, the contact angle of the image-receivinglayer with water is more preferably 89° or less. With the above range ofthe contact angle, transfer sensitivity can be enhanced and, further,the temperature-humidity dependency of recording characteristics can bedecreased.

[0120] The contact angle with water of each layer surface in the presentinvention is the value obtained by measuring by a contact angle meterCA-A type (manufactured by Kyowa Kaimen Kagaku Co., Ltd.).

[0121] In the next place, the system at large developed by the presentinventors will be described below together with the content of thepresent invention. In the system of the present invention, highdefinition and high image quality have been attained by adopting amembrane heat transfer system (i.e., a thin film heat transfer system).The system of the present invention is capable of obtaining atransferred image having definition of 2,400 dip or more, preferably2,600 dip or more. The heat transfer system by membrane (i.e., by thinfilm) is a system of transferring a thin image-forming layer having afilm thickness of from 0.01 to 0.9 μm to an image-receiving sheet in thestate of partially not melting or hardly melting. That is, since therecorded part is transferred as a membrane, an image of extremely highdefinition can be obtained. A preferred method of efficiently performingmembrane heat transfer is to deform the inside of a light-to-heatconverting layer to a dome-like form by heat-recording, push up theimage-forming layer, to thereby enhance the adhesion of theimage-forming layer and the image-receiving layer to make transferringeasy. When the deformation is large, transferring becomes easy, sincethe force of pressing the image-forming layer against theimage-receiving layer is great. While when the deformation is small,sufficient transferring cannot be effected in part, since the force ofpressing the image-forming layer against the image-receiving layer issmall. Deformation preferred for the membrane transfer can be observedby a laser microscope (VK8500, manufactured by Keyence Corporation), andthe size of deformation can be evaluated by a deformation factorobtained by dividing [increased cross-sectional area of the recordingarea of the light-to-heat converting layer after heat recording (a) pluscross-sectional area of the recording area of the light-to-heatconverting layer before heat recording (b)] by [cross-sectional area ofthe recording area of the light-to-heat converting layer before heatrecording (b)] and multiplying 100. That is, deformationfactor=[(a+b)/(b)]×100. The deformation factor is generally 110% ormore, preferably 125% or more, and more preferably 150% or more. Thedeformation factor maybe greater than 250% when the breaking elongationis made large but it is preferred to restrict the deformation factor toabout 250% or less.

[0122] The technical points of the image-forming material in membranetransfer are as follows.

[0123] 1. Compatibility of High Heat Responsibility and StorageStability

[0124] For obtaining high image quality, transferring of a membrane(i.e., a thin film) of sub-micron order is necessary, but for obtainingdesired density, it is necessary to form a layer having dispersedtherein a pigment in high concentration, which is reciprocal to heatresponsibility. Heat responsibility is also in the relationshipreciprocal to storage stability (adhesion). By the development of novelpolymer-additive, this reciprocal relationship has been solved.

[0125] 2. Security of High Vacuum Adhesion

[0126] In membrane transfer pursuing high definition, the interface oftransfer is preferably smooth, by which, however, sufficient vacuumadhesion cannot be obtained. Vacuum adhesion could be obtained by addinga little much amount of a matting agent having a relatively smallparticle size to the under layer of the image-forming layer, departingfrom general knowledge of obtaining vacuum adhesion, with maintainingproper gap uniform between the heat transfer sheet and theimage-receiving sheet, without causing clear spots of image and securingthe characteristics of membrane transfer.

[0127] 3. Use of Heat Resisting Organic Material

[0128] A light-to-heat converting layer which converts laser beam toheat at laser recording attains the temperature of about 700° C. and animage-forming layer containing pigment materials reaches about 500° C.The present inventors have developed, as the material of a light-to-heatconverting layer, modified polyimide capable of coating with an organicsolvent, and at the same time pigments which are higher heat resistingthan pigments for printing, safe and coincident in hue, as the pigmentmaterials.

[0129] 4. Security of Surface Cleanliness

[0130] In membrane transfer, dust between a heat transfer sheet and animage-receiving sheet causes an image defect, which is a seriousproblem. There are dust coming from the outside of the apparatus, orgenerated by cutting of materials, therefore dust cannot be excluded byonly material control, and it is necessary that apparatus must beprovided with a dust removing device. However, we found a materialcapable of maintaining appropriate viscosity and capable of cleaning thesurface of a transfer material and realized the removal of dust bychanging the material of the transfer roller without reducing theproductivity.

[0131] In the next place, the system at large of the present inventionwill be described in detail below.

[0132] The present invention has realized a heat transfer image havingsharp dots and transferring of an image to actual printing paper of arecording size of B2 size or larger (515 mm or more multiplying 728 mmor more). More preferably B2 size is 543 mm multiplying 765 mm(particularly 594 mm multiplying 841 mm), and recording of larger thanthis size is possible according to the present invention.

[0133] One characteristic of the performances of the system of thepresent invention is that sharp dot shape can be obtained. A heattransfer image obtained by this system is a dot image corresponding toprint line number of definition of 2,400 dpi or more. Since individualdot obtained according to this system is very sharp and almost free ofblur and chip, dots of a wide range from highlight to shadow can beclearly formed. As a result, output of dots of high grade having thesame definition as obtained by an image setter and a CTP setter ispossible, and dots and gradation which are excellent in approximation tothe printed matter can be reproduced.

[0134] The second characteristic of the performances of the system ofthe present invention is that repeating reproducibility is good. Since aheat transfer image obtained by this system is sharp in dot shape, dotscorresponding to laser beam can be faithfully reproduced, furtherrecording characteristics are hardly influenced by the surroundingtemperature and humidity, repeating reproducibility stable in hue anddensity can be obtained under wide temperature humidity conditions.

[0135] The third characteristic of the performances of the system of thepresent invention is that color reproduction is good. A heat transferimage obtained by this system is formed with coloring pigments used inprinting inks and since excellent in repeating reproducibility, highlyminute CMS (color management system) can be realized.

[0136] The heat transfer image by the system of the present inventionalmost coincided with the hues of Japan color and SWOP color, i.e., thehues of printed matters, and the colors appear similarly to the printedmatter even when light sources of illumination are changed, such as afluorescent lamp, an incandescent lamp.

[0137] The fourth characteristic of the performances of the system ofthe present invention is that the quality of a character is good. Sincea heat transfer image obtained by this system is sharp in dot shape, thefine line of a fine character can be reproduced sharply.

[0138] The characteristic technical points of the material for use inthe system of the present invention are further described in detailbelow. As the heat transfer methods for DDCP, there are (1) asublimation method, (2) an ablation method, and (3) a heat fusionmethod. Methods (1) and (2) are systems using sublimation or sputtering,the outline of a dot becomes fuzzy. On the other hand, inmethod(3),since a molten substance flows, the outline of a dot is notalso clear. On the basis of a membrane transfer technique, the presentinventors incorporated the following techniques to the system of thepresent invention for solving the new problems in laser transfer systemsand obtaining further high image quality. The first characteristic ofthe technique of materials is sharpening of dot shape. Image recordingis performed by converting laser beams to heat in a light-to-heatconverting layer and conducting the heat to the image-forming layercontiguous to the light-to-heat converting layer, and adhering theimage-forming layer to an image-receiving layer. For sharpening dotshape, heat generated by laser beams is not diffused in the surfacedirection but conducted to the transfer interface, and the image-forminglayer ruptures sharply at interface of heating area/non-heating area.The thickness of the light-to-heat converting layer in the heat transfersheet is thinned and dynamic properties of the image-forming layer arecontrolled for this purpose.

[0139] The first technique of sharpening of dot shape is thinning of thelight-to-heat converting layer. The light-to-heat converting layer ispresumed from simulation to reach about 700° C. in a moment, and a thinfilm is liable to be deformed and ruptured. When deformation andrupturing occur, the light-to-heat converting layer is transferred tothe image-receiving layer together with the image-forming layer or atransferred image becomes uneven. On the other hand, a light-to-heatconverting material must be present in the light-to-heat convertinglayer in high concentration for obtaining a desired temperature, whichresults in a problem of precipitation of the light-to-heat convertingmaterial or migration of the material to the contiguous layer. Carbonblack has been conventionally used in many cases as the light-to-heatconverting material, but an infrared absorbing dye is used as thelight-to-heat converting material in the present invention which cansave the use amount as compared with carbon black. Polyimide compoundshaving sufficient dynamic strength even at high temperature and highretentivity of an infrared absorbing dye were introduced as the binder.

[0140] In this manner, it is preferred to make thin the light-to-heatconverting layer up to about 0.5 μm or less by selecting an infraredabsorbing dye excellent in light-to-heat converting property and aheat-resisting binder such as polyimide compounds.

[0141] The second technique of sharpening of dot shape is theimprovement of the characteristics of an image-forming layer. When alight-to-heat converting layer is deformed or an image-forming layeritself is deformed due to high temperature, thickness unevenness iscaused in an image-forming layer transferred to an image-receiving layercorresponding to the subsidiary scanning pattern of laser beams, as aresult the image becomes uneven and apparent transfer density isreduced. The thinner the thickness of an image-forming layer, the moreconspicuous is this tendency. On the other hand, when the thickness ofan image-forming layer is thick, dot sharpness is impaired andsensitivity decreases.

[0142] To reconcile these reciprocal properties, it is preferred toimprove transfer unevenness by adding a low melting point material to animage-forming layer, e.g., a wax. Transfer unevenness can be improvedwith maintaining dot sharpness and sensitivity by adding inorganic fineparticles in place of a binder to adjust the layer thickness of animage-forming layer properly so that the image-forming layer rupturessharply at interface of heating area/non-heating area.

[0143] In general, materials having a low melting point, such as a wax,are liable to ooze out to the surface of an image-forming layer or to becrystallized and cause a problem in image quality and the agingstability of a heat transfer sheet in some cases.

[0144] To cope with this problem, it is preferred to use a low meltingpoint material having no great difference from the polymer of animage-forming layer in an SP (Solubility Parameter) value, by which thecompatibility with the polymer can be increased and the separation ofthe low melting point material from the image-forming layer can beprevented. It is also preferred to mix several kinds of low meltingpoint materials to prevent crystallization by eutectic mixture. As aresult, an image showing a sharp dot shape and free of unevenness can beobtained.

[0145] The second characteristic of the technique of the materials isthat the present inventors found that recording sensitivity hastemperature and humidity dependency. The dynamic properties and thermalphysical properties of the coated layers of a heat transfer sheet aregenerally varied by absorbing moisture and the humidity dependency ofrecording condition is caused.

[0146] For reducing the temperature and humidity dependency, it ispreferred that the dye/binder system of a light-to-heat converting layerand the binder system of an image-forming layer are organic solvents.Further, it is preferred to use polyvinyl butyral as the binder of animage-receiving layer and to introduce a hydrophobitization technique ofpolymers for the purpose of lowering water absorption properties ofpolymers. As the hydrophobitization technique of polymers, the techniqueof reacting a hydroxyl group with a hydrophobic group, or crosslinkingtwo or more hydroxyl groups with a hardening agent as disclosed inJP-A-8-238858 can be exemplified.

[0147] The third characteristic of the technique of the materials is theimprovement of the approximation of hue to the printed matter. Inaddition to color matching of pigments by thermal head system colorproof (First Proof, manufactured by Fuji Photo Film Co., Ltd.) and thetechnique of stable dispersion, a problem newly occurred in the laserheat transfer system was solved. That is, technique 1 of the improvementof the approximation of hue to the printed matter is to use a highlyheat resisting pigment. About 500° C. or more heat is generally appliedto an image-forming layer by laser exposure imaging, and so some ofconventionally used pigments are heat-decomposed, but this problem canbe prevented by using highly heat resisting pigments in an image-forminglayer.

[0148] Technique 2 of the improvement of the approximation of hue to theprinted matter is the diffusion prevention of an infrared absorbingmaterial. For preventing the variation of hue due to migration of aninfrared absorbing dye from a light-to-heat converting layer to animage-forming layer by high heat at exposure, it is preferred to designa light-to-heat converting layer by combination of an infrared absorbingdye having high retentivity and a binder as described above.

[0149] The fourth characteristic of the technique of the materials is toincrease sensitivity. Shortage of energy generally occurs in high speedprinting and, in particular, time lag is caused in intervals of lasersubsidiary-scanning and gaps are generated. As described above, using adye of high concentration in a light-to-heat converting layer andthinning of a light-to-heat converting layer and an image-forming layercan improve the efficiency of generation and conduction of heat. It isalso preferred to add a low melting point material to an image-forminglayer for the purpose of slightly fluidizing the image-forming layer atheating to thereby fill the gaps and improving the adhesion with theimage-receiving layer. Further, for enhancing the adhesion of theimage-receiving layer and the image-forming layer and sufficientlystrengthening a transferred image, it is preferred to use polyvinylbutyral used in the image-forming layer as the binder in theimage-receiving layer.

[0150] The fifth characteristic of the technique of the materials is theimprovement of vacuum adhesion. It is preferred that an image-receivingsheet and a heat transfer sheet are retained on a drum by vacuumadhesion. Since an image is formed by the adhesion control of bothsheets, image transfer behavior is very sensitive to the clearancebetween the image-receiving layer surface in an image-receiving sheetand the image-forming layer surface in a transfer sheet, hence vacuumadhesion is important. If the clearance between the materials is widenedwith foreign matter, e.g., dust, as a cue, image defect and imagetransfer unevenness come to occur.

[0151] For preventing such image defect and image transfer unevenness,it is preferred to give uniform unevenness to a heat transfer sheet tothereby improve the air passage, to obtain uniform clearance.

[0152] Technique 1 of the improvement of vacuum adhesion is theprovision of unevenness to the surface of a heat transfer sheet. Forobtaining sufficient effect of vacuum adhesion even in superposedprinting of two or more colors, unevenness is provided to a heattransfer sheet. For providing unevenness to a heat transfer sheet, amethod of post treatment such as embossing treatment and a method ofaddition of a matting agent to a coating layer are generally used, butin view of the simplification of manufacturing process and stabilizationof materials with the lapse of time, addition of a matting agent ispreferred. The particle size of a matting agent must be larger than thethickness of the coating layer. When a matting layer is added to animage-forming layer, there arises a problem of coming out of the imageof the part where the matting layer is present, accordingly, it ispreferred to add a matting agent having an optimal particle size,thereby the layer thickness of the image-forming layer becomes almostuniform and an image free of defect can be obtained on theimage-receiving sheet.

[0153] The characteristics of the technique of systematization of thesystem of the present invention are described below. The firstcharacteristics of the technique of systematization is the constitutionof a recording unit. For surely reproducing sharp dots as describedabove, highly precise design is required also for a recording unit. Therecording unit for use in the system of the present invention is thesame as conventionally used recording units for laser heat transfer infundamental constitution. The constitution is a so-called heat modeouter drum recording system and recording is performed such that arecording head provided with a plurality of high power lasers emit laserrays on a heat transfer sheet and an image-receiving sheet fixed on adrum. A preferred embodiment is as follows.

[0154] Constitution 1 of a recording unit is to prevent mixing of dust.Feeding of an image-receiving sheet and a heat transfer sheet isperformed by full automatic roll feeding. Mixture of dusts generatedfrom the human body cannot be helped by sheet feeding of a small number,thus roll feeding is adopted.

[0155] Since heat transfer sheet comprises four colors each one roll, aroll of each color is switched to another by a rotating loading unit.Each film is cut to a prescribed length by a cutter during loading andfixed on a drum. Constitution 2 of a recording unit is to enhance theadhesion of an image-receiving sheet and a heat transfer sheet on arecording drum. The adhesion of an image-receiving sheet and a heattransfer sheet on a recording drum is vacuum adhesion, since theadhesion of an image-receiving sheet and a heat transfer sheet cannot bestrengthened by mechanical fixing. Many vacuum suction holes are formedon a recording drum, and a sheet is sucked by a drum by reducing thepressure in a drum with a blower or a decompression pump. Since a heattransfer sheet is further sucked over the sucked image-receiving sheet,the size of the heat transfer sheet is made larger than the size of theimage-receiving sheet. The air between the heat transfer sheet and theimage-receiving sheet which most affects recording performance is suckedfrom the area outside of the image-receiving sheet where the heattransfer sheet is alone.

[0156] Constitution 3 of a recording unit is accumulation of multisheets of films on a discharge-receiving table stably. In the apparatusof the present invention, a multi sheets of large sized films of B2 sizeor larger can be accumulated on the discharge-receiving table. Whensheet B is discharged on the image-receiving layer of the alreadyaccumulated heat-adhesive film A, sometimes both cleave to each other.When the previous sheet cleaves to the previous of the previous sheet,the next sheet cannot be discharged correctly, which leads to theproblem of jamming. For preventing cleaving, the prevention of thecontact of film A and film B is the best. Some means are known as thecontact preventing method, e.g., (a) a method of making difference indischarge-receiving table level to make a gap between films by makingfilm shape not plane, (b) a method of providing discharge port at higherposition than discharge-receiving table and dropping a discharged film,and (c) a method of floating the film discharged later by blasting airbetween two films. In the system of the present invention, as the sheetsize is very big (B2), the structures of units are large scaled whenmethods (a) and (b) are used, hence, (c) a method of floating the filmdischarged later by blasting air between two films is adopted.

[0157] An example of constitution of the apparatus of the presentinvention is shown in FIG. 2.

[0158] The sequence of forming a full color image by applying animage-forming material to the apparatus of the present invention(hereinafter referred to as image-forming sequence of the system of thepresent invention) is described below.

[0159] 1) Subsidiary scanning axis of recording head 2 of recording unit1 is reset by subsidiary scanning rail 3, main scan rotation axis ofrecording drum 4 and heat transfer sheet loading unit 5 are respectivelyreset at origin.

[0160] 2) Image-receiving sheet roll 6 is unrolled by carrier roller 7,and the tip of the image-receiving roll is fixed on recording drum 4 byvacuum suction (i.e., vacuum drawing) via suction holes provided on therecording drum.

[0161] 3) Squeeze roller 8 comes down on recording drum 4 and pressesthe image-receiving sheet, and when the prescribed amount of theimage-receiving sheet is conveyed by the rotation of the drum, the sheetis stopped and cut by cutter 9 in a prescribed length.

[0162] 4) Recording drum 4 further makes a round, thus the loading ofthe image-receiving sheet is finished.

[0163] 5) In the next place, in the same sequence as the image-receivingsheet, heat transfer sheet K of the first color, black, is drawn outfrom heat transfer sheet roll 10K, cut and loaded.

[0164] 6) Recording drum 4 starts high speed rotation, recording head 2on subsidiary scanning rail 3 starts to move and when reaches the startposition of recording, recording laser is emitted on recording drum 4 byrecording head 2 according to recording signals. Irradiation is finishedat finishing position of recording, operation of subsidiary scanningrail and drum rotation are finished. The recording head on thesubsidiary scanning rail is reset.

[0165] 7) Only heat transfer sheet K is peeled with the image-receivingsheet remaining on the recording drum. For the peeling , the tip of heattransfer sheet K is caught by the claw, pulled out in the dischargedirection, and discarded from discard port 32 to discard box 35.

[0166] 8) The procedures of 5) to 7) are repeated for the remainingthree colors. Recording is performed in the order of black, cyan,magenta and yellow. That is, heat transfer sheet C of the second color,cyan, is drawn out from heat transfer sheet roll 10C, heat transfersheet M of the third color, magenta, is from heat transfer sheet roll10M, and heat transfer sheet Y of the fourth color, yellow, is from heattransfer sheet roll 10Y in order. This is the inverse of generalprinting order, since the order of the colors on actual paper becomesinverse by the later process of transfer to actual paper.

[0167] 9) After recording of four colors, the recorded image-receivingsheet is discharged to discharge-receiving table 31. The peeling methodfrom the drum is the same as that of the heat transfer sheet in above7), but since the image-receiving sheet is not discarded differentlyfrom the heat transfer sheets, the image-receiving sheet is returned tothe discharge-receiving table by switch back when conveyed to discardport 32. When the image-receiving sheet is discharged to thedischarge-receiving table, air 34 is blasted from under discharge port33 to make it possible to accumulate a plurality of sheets.

[0168] It is preferred to use an adhesive roller provided with anadhesive material on the surface as carrier roller 7 of either feedingpart or carrying part of the heat transfer sheet roll and theimage-receiving sheet roll.

[0169] The surfaces of the heat transfer sheet and the image-receivingsheet can be cleaned by providing an adhesive roller.

[0170] As the adhesive materials provided on the surface of the adhesiveroller, an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylatecopolymer, a polyolefin resin, a polybutadiene resin, astyrene-butadiene copolymer (SBR), a styrene-ethylene-butene-styrenecopolymer (SEBS), an acrylonitrile-butadiene copolymer (NBR), apolyisoprene resin (IR), a styrene-isoprene copolymer (SIS), an acrylicester copolymer, a polyester resin, a polyurethane resin, an acrylateresin, a butyl rubber, and a polynorbornene can be exemplified.

[0171] An adhesive roller can clean the surfaces of the heat transfersheet and the image-receiving sheet by being brought into contact withthe surfaces of them, and the contact pressure is not particularlylimited so long as they are in contact with the adhesive roller.

[0172] Vickers hardness Hv of the material having viscosity used in theadhesive roller is preferably 50 kg/mm² (=about 490 MPa) or less in viewof capable of sufficiently removing foreign matters and suppressingimage defect.

[0173] Vickers hardness is hardness obtained by measurement withapplying static load to a pyramid indenter of diamond having the anglebetween the opposite faces of 136°, and Vickers hardness Hv can beobtained by the following equation:

Hardness Hv=1.854 P/d ² (kg/mm ²)=about 18.1692 P/d ² (Mpa)

[0174] wherein P: load (kg), d: the length of diagonal line of thesquare of depressed area (mm).

[0175] Also in the present invention, the modulus of elasticity at 20°C. of the material having viscosity used in the adhesive roller ispreferably 200 kg/cm² (=about 19.6 MPa) or less in view of capable ofsufficiently removing foreign matters and suppressing image defectsimilarly to the above.

[0176] The second characteristics of the technique of systematization isthe constitution of the heat transfer unit.

[0177] The heat transfer unit is used for the steps of transferring theimage-receiving sheet on which an image has been printed with arecording unit to an actual printing paper (hereinafter referred to as“actual paper”). This step is completely the same with First Proof™.When the image-receiving sheet and an actual paper are superposed andheat and pressure are applied thereto, both are adhered, and then theimage-receiving film is peeled from the actual paper, an image and theadhesion layer remain on the actual paper, and the support of theimage-receiving sheet and the cushioning layer are peeled off.Accordingly, it can be said that the image is transferred from theimage-receiving sheet to the actual paper in practice.

[0178] In First Proof™, transferring is performed by super-posing anactual paper and an image-receiving sheet on an aluminum guide plate andpassing them through a heat roller. The aluminum guide plate is forpreventing the deformation of the actual paper. However, when analuminum guide plate is adopted in the system of the present inventionof B2 size, an aluminum guide plate larger than B2 size is necessary,which results in the problem that a large installation space isrequired. Accordingly, the system of the present invention does not usean aluminum guide plate and adopts the structure such that a carrierpath rotates in a 180° arc and sheets are discharged on the side ofinsertion, thus the installation space can be largely saved (FIG. 3).However, there arises a problem of the deformation of an actual paper,since an aluminum guide plate is not used. Specifically, a pair of anactual paper and an image-receiving sheet curl with the image-receivingsheet inside and roll on the discharge-receiving table. It is verydifficult work to peel the image-receiving sheet from the curled actualpaper.

[0179] Therefore, curling prevention is tried by bimetallic effect bymaking use of the difference in shrinking amount between an actual paperand an image-receiving sheet and ironing effect of winding them around ahot roller. In the case where an image-receiving sheet is superposed onan actual paper and inserted as in conventional way, since the thermalshrinkage of an image-receiving sheet in the direction of insertion islarger than that of an actual paper, curling by bimetallic effect issuch that the upper tends inward, which is the same direction as in theironing effect and curling becomes serious by synergistic effect.Contrary to this, when an image-receiving sheet is superposed under anactual paper, curling by bimetallic effect tends downward and curling byironing effect tends upward, thus curls are offset each other.

[0180] The sequence of an actual paper transfer is as follows(hereinafter referred to as the transfer method of an actual paper foruse in the system of the present invention). Heat transfer unit 41 foruse in this method as shown in FIG. 3 is a manual apparatus differentlyfrom a recording unit.

[0181] 1) In the first place, the temperature of heat rollers 43 (from100 to 110° C.) and the carrying velocity at transferring are set bydials (not shown) according to the kind of actual paper 42.

[0182] 2) In the next place, image-receiving sheet 20 is put on aninsert-receiving table with the image being upward, and the dust on theimage is removed by an antistatic brush (not shown). Actual paper 42from which dust has been removed is superposed thereon. At that time,since the size of actual paper 42 put upper side is larger thanimage-receiving sheet 20 put lower side, the position of image-receivingsheet 20 is not seen and alignment is difficult to do. For improvingthis work, marks showing the positions of placement of animage-receiving sheet and an actual paper 45 are marked oninsert-receiving table 44. The reason the actual paper is larger thanimage-receiving sheet 20 is to prevent image-receiving sheet 20 fromdeviating and coming out from actual paper 42 and prevent theimage-receiving layer of image-receiving sheet 20 from staining heatrollers 43.

[0183] 3) The image-receiving sheet and the actual paper with beingsuperposed are inserted into an insert port, and insert roller 46rotates and feeds them to heat rollers 43.

[0184] 4) When the tip of the actual paper comes to the position of heatrollers 43, the heat rollers nip them and transfer is started. The heatrollers are heat resisting silicone rubber rollers. Pressure and heatare applied simultaneously to the image-receiving sheet and the actualpaper, thereby they are adhered. Guide 47 made of heat resisting sheetis installed on the down stream of the heat rollers, and a pair of theimage-receiving sheet and the actual paper is carried upward through theupper heat roller and guide 47 with heating, they are peeled from theheat roller at peeling claw 48 and guided to discharge port 50 alongguide plate 49.

[0185] 5) A pair of the image-receiving sheet and the actual papercoming out of discharge port 50 is discharged on the insert-receivingtable with being adhered. Thereafter, image-receiving sheet 20 is peeledfrom actual paper 42 manually.

[0186] The second characteristics of the technique of systematization isthe constitution of the system.

[0187] By connecting the above units with aplate-making system, thefunction as color proof can be exhibited. As the system, it is necessarythat a printed matter having an image quality approximating as far aspossible to the printed matter outputted from certain plate-making datamust be outputted from a proof. Therefore, a software for approximatingdots and colors to the printed matter is necessary. The specific exampleof connection is described below.

[0188] When the proof of a printed matter is taken from the plate-makingsystem Celebra™ (manufactured by Fuji Photo Film Co., Ltd.), the systemconnection is as follows. CTP (computer to plate) system is connectedwith Celebra. The final printed matter can be obtained by mounting theprinting plate outputted from this system on a printing machine. As acolor proof, the above recording unit Luxel FINALPROOF 5600(manufactured by Fuji Photo Film Co., Ltd.) (hereinafter sometimes alsoreferred to as “FINALPROOF”) is connected with Celebra, and as proofdrive software for approximating dots and colors to the printed matter,PD SYSTEM™ (manufactured by Fuji Photo Film Co., Ltd.) is also connectedwith Celebra.

[0189] Contone data (continuous tone data) converted to raster data byCelebra are converted to binary data for dots and out putted to CTPsystem and finally printed. On the other hand, the same contone data arealso outputted to PD system. PD system converts the received dataaccording to four dimensional (black, cyan, magenta and yellow) table sothat the colors coincide with the printed matter, and finally convertsto binary data for dots so that the dots coincide with the dots of theprinted matter and the data is outputted to FINALPROOF (FIG. 4).

[0190] The four dimensional table is experimentally prepared in advanceand saved in the system. The experiment for the preparation of the fourdimensional table is as follows. The printed image of important colordata via CTP system and the outputted image of important color data fromFINALPROOF via PD system are prepared, the measured color values ofthese images are compared and the table is formed so that the differencebecomes minimum.

[0191] Thus, the present invention has realized the system constitutionwhich can sufficiently exhibit the performance of the image-formingmaterial having high definition.

[0192] The material of the heat transfer system for use in the system ofthe present invention is described below.

[0193] It is preferred that the absolute value of the difference betweenthe surface roughness Rz of the front surface of the image-forming layerin the heat transfer sheet and the surface roughness Rz of the backsurface of the image-forming layer is 3.0 or less, and absolute value ofthe difference between the surface roughness Rz of the front surface ofthe image-receiving layer in the image-receiving sheet and the surfaceroughness Rz of the back surface of the image-receiving layer is 3.0 orless. By such constitution of the present invention, conjointly with theabove cleaning means, image defect can be prevented, jamming in carryingcan be done away with, and dot gain stability can be improved.

[0194] The surface roughness Rz in the present invention means ten pointaverage surface roughness corresponding to Rz (maximum height) definedin JIS B 0601. The surface roughness is obtained by inputting andcomputing the distance between the average value of the altitudes offrom the highest peak to the fifth peak and the average value of thedepths of from the deepest valley to the fifth valley. A feeler typethree dimensional roughness meter (Surfcom 570A-3DF, manufactured byTokyo Seimitsu Co., Ltd.) is used in measurement. The measurement isperformed in machine direction, the cutoff value is 0.08 mm, themeasured area is 0.6 mm×0.4 mm, the feed pitch is 0.005 mm, and thespeed of measurement is 0.12 mm/sec.

[0195] For further improving the above-described effects, it is morepreferred that the absolute value of the difference between the surfaceroughness Rz of the front surface of the image-forming layer in the heattransfer sheet and the surface roughness Rz of the back surface of theimage-forming layer is 1.0 or less, and absolute value of the differencebetween the surface roughness Rz of the front surface of theimage-receiving layer in the image-receiving sheet and the surfaceroughness Rz of the back surface of the image-receiving layer is 1.0 orless.

[0196] Further, as another embodiment, it is preferred that the surfaceroughness Rz of the front surface and the back surface of the heattransfer sheet and/or the surface roughness Rz of the front surface andthe back surface of the image-receiving sheet is from 2 to 30 μm. Bysuch constitution of the present invention, conjointly with the abovecleaning means, image defect can be prevented, jamming in carrying canbe done away with, and dot gain stability can be improved.

[0197] It is also preferred that the glossiness of the image-forminglayer in the heat transfer sheet is from 80 to 99.

[0198] The glossiness largely depends upon the surface smoothness of theimage-forming layer and can affect the uniformity of the layer thicknessof the image-forming layer. When the glossiness is higher, theimage-forming layer becomes more uniform and more preferred for highlyminute use, but when the smoothness is high, the resistance at conveyingbecomes larger, thus they are in relationship of trade off. When theglossiness is from 80 to 99, both are compatible and well-balanced.

[0199] The scheme of multicolor image-forming by membrane heat transfer(i.e., thin film heat transfer) using a laser is described withreferring to FIG. 1.

[0200] Laminate 30 for image formation comprising image-receiving sheet20 laminated on the surface of image-forming layer 16 containing pigmentblack (K), cyan (C), magenta (M) or yellow (Y) in heat transfer sheet 10is prepared. Heat transfer sheet 10 comprises support 12, havingprovided thereon light-to-heat converting layer 14 and further thereonimage-forming layer 16, image-receiving sheet 20 comprises support 22and having provided thereon image-receiving layer 24, andimage-receiving layer 24 is laminated on the surface of image-forminglayer 16 in heat transfer sheet 10 in contact therewith (FIG. 1(a)).When laser beams are emitted imagewise in time series from the side ofsupport 12 in heat transfer sheet 10 of laminate 30, the irradiated areawith laser beams of light-to-heat converting layer 14 in heat transfersheet 10 generates heat, thereby the adhesion with image-forming layer16 is reduced (FIG. 1(b)). Thereafter, when image-receiving sheet 20 andheat transfer sheet 10 are peeled off, the area irradiated with laserbeams 16′ of image-forming layer 16 is transferred to image-receivinglayer 24 in image-receiving sheet 20 (FIG. 1(c)).

[0201] In multicolor image formation, the laser beam for use inirradiation preferably comprises multi-beams, particularly preferablycomprises multi-beams of two-dimensional array. Multi-beams oftwo-dimensional array means, a plurality of laser beams are used whenrecording by irradiation with laser beam is performed, and the spotarray of these laser beams comprises two-dimensional array comprised ofa plurality of rows along the main scanning direction and a plurality ofrows along the subsidiary scanning direction.

[0202] The time required in laser recording can be shortened by usingmulti-beams of two-dimensional array.

[0203] Any laser beam can be used in recording with no limitation, suchas gas laser beams, e.g., an argon ion laser beam, a helium neon laserbeam, and a helium cadmium laser beam, solid state laser beams, e.g., aYAG laser beam, and direct laser beams, e.g., a semiconductor laserbeam, a dye laser beam and an eximer laser beam, can be used.Alternatively, laser beams obtained by converting these laser beams tohalf the wavelength through second harmonic generation elements can alsobe used. In multicolor image formation, semiconductor laser beams arepreferably used taking the output power and easiness of modulation intoconsideration. In multicolor image formation, it is preferred that laserbeam emission is performed on conditions that the beam diameter of laserbeam on the light-to-heat converting layer is from 5 to 50 μm (inparticular from 6 to 30 μm), and scanning speed is preferably 1 m/secondor more (particularly preferably 3 m/second or more).

[0204] In addition, it is preferred in multicolor image formation thatthe layer thickness of the image-forming layer in the black heattransfer sheet is larger than the layer thickness of the image-forminglayer in each of yellow, magenta and cyan heat transfer sheet, and ispreferably from 0.5 to 0.7 μm. By adopting this constitution, thereduction of density due to transfer unevenness by the irradiation ofthe black heat transfer sheet with laser beams can be suppressed.

[0205] By restricting the layer thickness of the image-forming layer inthe black heat transfer sheet to 0.5 μm or more, transfer unevenness isnot generated by high energy recording and image density is maintained,thus required image density as the proof of printing can be attained.This tendency becomes more conspicuous under high humidity conditions,and so density variation due to circumferential conditions can beprevented. On the other hand, by making the layer thickness 0.7 μm orless, transfer sensitivity can be maintained at recording time by laserand touching of dots and fine lines can be improved. This tendencybecomes more conspicuous under low humidity conditions. Definition canalso be improved by the layer thickness of this range. The layerthickness of the image-forming layer in the black heat transfer sheet ismore preferably from 0.55 to 0.65 μm and particularly preferably 0.60μm.

[0206] Further, it is preferred that the layer thickness of theimage-forming layer in the above black heat transfer sheet is from 0.5to 0.7 μm, and the layer thickness of the image-forming layer in each ofthe above yellow, magenta and cyan heat transfer sheets is from 0.2 toless than 0.5 μm.

[0207] By making the layer thickness of each image-forming layer inyellow, magenta and cyan heat transfer sheets 0.2 μm or more, imagedensity can be maintained without generating transfer unevenness whenrecording is performed by laser irradiation. On the other hand, bymaking the layer thickness less than 0.5 μm, transfer sensitivity anddefinition can be improved. The layer thickness of the image-forminglayer in yellow, magenta and cyan heat transfer sheets is morepreferably from 0.3 to 0.45 μm.

[0208] It is preferred for the image-forming layer in the black heattransfer sheet to contain carbon black, and the carbon black preferablycomprises at least two carbon blacks having different tinting strengthfrom the viewpoint of capable of controlling reflection density withmaintaining P/B (pigment/binder) ratio in a specific range.

[0209] The tinting strength of carbon black can be representedvariously, e.g., PVC blackness disclosed in JP-A-10-140033, can beexemplified. PVC blackness is the evaluation of blackness, i.e., carbonblack is added to PVC resin, dispersed by a twin roll mill and made to asheet, and the blackness of a sample is evaluated by visual judgement,with taking the blackness of Carbon Black #40 and #45 (manufactured byMitsubishi Chemicals Co., Ltd.) as 1 point and 10 points respectively asthe standard values. Two or more carbon black shaving different PVCblackness can be used arbitrarily according to purposes.

[0210] The specific producing method of a sample is described below.

[0211] Producing Method of Sample

[0212] In a banbury mixer having a capacity of 250 ml, 40 mass % (i.e.,weight %) of sample carbon black was compounded to LDPE (low densitypolyethylene) resin and kneaded at 115° C. for 4 minutes. Compoundingcondition LDPE resin 101.89 g Calcium stearate  1.39 g Irganox ® 1010 0.87 g Sample carbon black  69.43 g

[0213] In the next place, dilution was performed in a twin roll mill at120° C. so as to reach the concentration of carbon black of 1 mass %.Preparation condition of diluted compound LDPE resin 58.3 g Calciumstearate  0.2 g Resin compounded with 40 mass % of carbon black  1.5 g

[0214] The above-prepared product was made to s sheet having a slitwidth of 0.3 mm, the sheet was cut to chips, and a film having athickness of 65±3 μm was formed on a hot plate at 240° C.

[0215] A multicolor image may be formed, as described above, by themethod of using the heat transfer sheet, and repeatedly superposing manyimage layers (an image-forming layer on which an image is formed) on thesame image-receiving sheet, alternatively a multicolor image may beformed by the method of forming images on a plurality of image-receivingsheet once, and then transferring these images to actual paper.

[0216] With the latter case, for example, heat transfer sheets eachhaving image-forming layer containing coloring material mutuallydifferent in hue are prepared, and independently four kinds (cyan,magenta, yellow, black) of laminates for image-forming comprising theabove heat transfer sheet combined with an image-receiving sheet areproduced. Laser emission according to digital signals on the basis ofthe image is performed to each laminate through a color separationfilter, subsequently the heat transfer sheet and the image-receivingsheet are peeled off, to thereby form independently a color separatedimage of each color on each image-receiving sheet. Thereafter, thethus-formed each color separated image is laminated in sequence on anactual support, such as actual printing paper prepared separately, or ona support approximates thereto, thus a multicolor image can be formed.

[0217] It is preferred for the heat transfer sheet utilizing laserirradiation to form an image by the system of converting laser beams toheat and membrane transferring the image-forming layer containing apigment on the image-receiving sheet using the above converted heatenergy. However, these techniques used for the development of theimage-forming material comprising the heat transfer sheet and theimage-receiving sheet can be arbitrarily applied to the development ofthe heat transfer sheets of a heat fusion transfer system, an ablationtransfer system, and sublimation system and/or the development of animage-receiving sheet, and the system of the present invention mayinclude image-forming materials used in these systems.

[0218] A heat transfer sheet and an image-receiving sheet are describedbelow in detail.

[0219] Heat Transfer Sheet

[0220] A heat transfer sheet comprises a support having thereon at leasta light-to-heat converting layer and an image-receiving layer, and, ifnecessary, other layers.

[0221] Support

[0222] The materials of the support of the heat transfer sheet are notparticularly restricted, and various supports can be used according topurposes. The support preferably has stiffness, good dimensionalstability, and heat resistance capable of resisting the heat at imageformation. The preferred examples of the support include syntheticresins, e.g., polyethylene terephthalate, polyethylene-2,6-naphthalate,polycarbonate, polymethyl methacrylate, polyethylene, polypropylene,polyvinyl chloride, polyvinylidene chloride, polystyrene,styrene-acrylonitrile copolymer, polyamide (aromatic and aliphatic),polyimide, polyamideimide, and polysulfone. Biaxially stretchedpolyethylene terephthalate is preferred above all from the viewpoint ofmechanical strength and dimensional stability against heat. When resinsare used in the preparation of color proofs utilizing laser recording,it is preferred to form the support of a heat transfer sheet fromtransparent synthetic resins which transmit laser beams. The thicknessof the support is preferably from 25 to 130 μm, particularly preferablyfrom 50 to 120 μm. The central line average surface roughness Ra of thesupport of the side on which an image-forming layer is provided ispreferably less than 0.1 μm (the value obtained by measurement usingSurfcom, manufactured by Tokyo Seiki Co., Ltd., according to JIS B0601).The Young's modulus of the support in the machine direction ispreferably from 200 to 1,200 kg/mm² (=about 2 to 12 GPa), and theYoung's modulus of the support in the transverse direction is preferablyfrom 250 to 1,600 kg/mm² (=about 2.5 to 16 GPa). The F-5 value of thesupport in the machine direction is preferably from 5 to 50 kg/mm²(=about 49 to 490 MPa), and the F-5 value of the support in thetransverse direction is preferably from 3 to 30 kg/mm² (=about 29.4 to294 MPa), and the F-5 value of the support in the machine direction isgenerally higher than the F-5 value of the support in the transversedirection, but when it is necessary to make the strength particularly inthe transverse direction high, this rule does not apply to the case.Further, the heat shrinkage at 100° C. for 30 minutes of the support inthe machine direction is preferably 3% or less, more preferably 1.5% orless, the heat shrinkage at 80° C. for 30 minutes is preferably 1% orless, more preferably 0.5% or less. The breaking strength is from 5 to100 kg/mm² (=about 49 to 980 MPa) in both directions, and the modulus ofelasticity is preferably from 100 to 2,000 kg/mm² (=about 0.98 to 19.6GPa).

[0223] The support of the heat transfer sheet may be subjected tosurface activation treatment and/or one or two or more undercoat layersmay be provided on the support for the purpose of improving the adhesionwith the light-to-heat converting layer which is provided on thesupport. As the examples of the surface activation treatments, glowdischarge treatment and corona discharge treatment can be exemplified.As the materials of the undercoat layer, materials having high adheringproperty to both surfaces of the support and the light-to-heatconverting layer, low heat conductivity, and excellent heat resistingproperty are preferably used. As the materials of such an undercoatlayer, styrene, a styrene-butadiene copolymer and gelatin can beexemplified. The thickness of the undercoat layer is generally from 0.01to 2 μm as a whole. If necessary, various functional layers such as areflection-preventing layer and an antistatic layer may be provided onthe surface of the heat transfer sheet of the side opposite to the sideon which a light-to-heat converting layer is provided, or the supportmay be subjected to various surface treatments.

[0224] Backing Layer

[0225] It is preferred to provide a backing layer on the surface of theheat transfer sheet of the side opposite to the side on which alight-to-heat converting layer is provided. The backing layer preferablycomprises the first backing layer contiguous to the support and thesecond backing layer provided on the side of the support opposite to theside on which the first backing layer is provided. In the presentinvention, the mass (i.e., the weight) A of the antistatic agentcontained in the first backing layer to the mass (i.e., the weight) theB of the antistatic agent contained in the second backing layer, B/A ispreferably less than 0.3. When B/A is 0.3 or more, a sliding propertyand powder dropout resistance of the backing layer are liable to bedeteriorated.

[0226] The layer thickness C of the first backing layer is preferablyfrom 0.01 to 1 μm, more preferably from 0.01 to 0.2 μm. The layerthickness D of the second backing layer is preferably from 0.01 to 1 μm,more preferably from 0.01 to 0.2 μm. The ratio of the layer thickness ofthe first backing layer to that of the second backing layer, C/D ispreferably from 1/2 to 5/1.

[0227] As the antistatic agents for use in the first and second backinglayers, a nonionic surfactant, e.g., polyoxyethylene alkylamine,andglycerol fatty acidester; a cationic surfactant, e.g., quaternaryammonium salt; an anionic surfactant, e.g., alkylphosphate; anampholytic surfactant and electrically conductive resin can beexemplified.

[0228] Electrically conductive fine particles can also be used asantistatic agents. The examples of such electrically conductive fineparticles include oxides, e.g., ZnO, TiO₂, SnO₂, Al₂O₃, In₂O₃, MgO, BaO,CoO, CuO, Cu₂O, CaO, SrO, BaO₂, PbO, PbO₂, MnO₃, MoO₃, SiO₂, ZrO₂, Ag₂O,Y₂O₃, Bi₂O₃, Ti₂O₃, Sb₂O₃, Sb₂O₅, K₂Ti₆O₃, NaCaP₂O₁₈ and MgB₂O₅;sulfide, e.g., CuS and ZnS; carbide, e.g., SiC, TiC, ZrC, VC, NbC, MoCand WC; nitride, e.g., Si₃N₄, TiN, ZrN, VN, NbN and Cr₂N; boride, e.g.,TiB₂, ZrB₂, NbB₂, TaB₂, CrB, MoB, WB and LaB₅; silicide, e.g., TiSi₂,ZrSi₂, NbSi₂, TaSi₂, CrSi₂, MoSi₂ and WSi₂; metal salts, e.g., BaCO₃,CaCO₃, SrCO₃, BaSO₄andCaSO₄; andcomposite, e.g., SiN₄—SiC and9Al₂O₃—2B₂O₃. These electrically conductive fine particles may be usedalone or in combination of two or more. Of these fine particles, SnO₂,ZnO, Al₂O₃, TiO₂, In₂O₃, MgO, BaO and MoO₃ are preferred, SnO₂, ZnO,In₂O₃ and TiO₂ are more preferred, and SnO₂ is particularly preferred.

[0229] When the heat transfer sheet of the present invention is used ina laser heat transfer system, the antistatic agent used in the backinglayer is preferably substantially transparent so that laser beams can betransmitted.

[0230] When electrically conductive metallic oxides are used as theantistatic agent, their particle size is preferably smaller to makelight scattering as small as possible, but the particle size should bedetermined using the ratio of the refractive indices of the particlesand the binder as parameter, which can be obtained according to thetheory of Mie. The average particle size of the electrically conductivemetallic oxides is generally from 0.001 to 0.5 μm, preferably from 0.003to 0.2 μm. The average particle size used herein is the value of theparticle size of not only the primary particles of the electricallyconductive metallic oxides but the particle size of the particles havingthe (hkl) structure is included.

[0231] Besides an antistatic agent, the first and secondbacking layersmay contain various additives, such as a surfactant, a sliding agent anda matting agent, and a binder. The amount of the antistatic agentcontained in the first backing layer is preferably from 10 to 1,000 massparts (i.e., weight parts) per 100 mass parts (i.e., weight parts) ofthe binder, more preferably from 200 to 800 mass parts. The amount ofthe antistatic agent contained in the second backing layer is preferablyfrom 0 to 300 mass parts per 100 mass parts of the binder, morepreferably from 0 to 100 mass parts.

[0232] As the binders for use for forming the first and second backinglayers, homopolymers and copolymers of acrylic acid-based monomers,e.g., acrylic acid, methacrylic acid, acrylic ester and methacrylicester, cellulose-based polymers, e.g., nitrocellulose, methyl cellulose,ethyl cellulose and cellulose acetate, vinyl-basedpolymers andcopolymers of vinyl compounds, e.g., polyethylene, polypropylene,polystyrene, vinyl chloride-based copolymer, vinyl chloride-vinylacetate copolymer, polyvinyl pyrrolidone, polyvinyl butyral andpolyvinyl alcohol, condensed polymers, e.g., polyester, polyurethane andpolyamide, rubber-based thermoplastic polymers, e.g., butadiene-styrenecopolymer, polymers obtained by polymerization or crosslinking ofphotopolymerizable or heat polymerizable compounds, e.g., epoxycompounds, and melamine compounds can be exemplified. Light-to-heatconverting layer The light-to-heat converting layer may contain alight-to-heat converting material, a binder, and other additives, ifnecessary.

[0233] Alight-to-heat converting material is a material having afunction of converting irradiated light energy to heat energy. Alight-to-heat converting material is in general a dye (inclusive of apigment, hereinafter the same) capable of absorbing a laser beam. Whenimage-recording is performed by infrared laser irradiation, it ispreferred to use an infrared absorbing dye as the light-to-heatconverting material. As the examples of the dyes, black pigments, e.g.,carbon black, pigments of macrocyclic compounds having absorption in thevisible region to the near infrared region, e.g., phthalocyanine andnaphthalocyanine, organic dyes which are used as the laser-absorbingmaterial in high density laser recording such as a magneto-optical disc,e.g., a cyanine dye such as an indolenine dye, an anthraquinone dye, anazulene dye and a phthalocyanine dye, and organic metallic compounddyes, e.g., dithiol nickel complex, can be exemplified. Of the abovecompounds, cyanine dyes are particularly preferably used, since theyshow a high absorption coefficient to the lights in the infrared region,and the thickness of a light-to-heat converting layer can be thinnedwhen used as the light-to-heat converting material, as a result, therecording sensitivity of a heat transfer sheet can be further improved.

[0234] As the light-to-heat converting material, particulate metallicmaterials such as blackened silver and inorganic materials can also beused besides dyes.

[0235] As the binder to be contained in the light-to-heat convertinglayer, resins having at least the strength capable of forming a layer ona support and preferably having high heat conductivity. Heat resistingresins which are not decomposed by heat generated from the light-to-heatconverting material at image recording are preferably used as the binderresin, since the surface smoothness of the light-to-heat convertinglayer can be maintained after irradiation even when light irradiation isperformed with high energy. Specifically, resins having heatdecomposition temperature (temperature at which the mass (i.e., theweight) decreases by 5% in air current at temperature increasingvelocity of 10° C./min by TGA method (thermal mass spectrometry)) of400° C. or more are preferably used, more preferably 500° C. or more.Binders preferably have glass transition temperature of from 200 to 400° C., more preferably from 250 to 350° C. When the glass transitiontemperature is lower than 200° C., there is a case where fog isgenerated on the image to be formed, while when it is higher than 400°C., the solubility of the resin is decreased, followed by the reductionof the productivity in some cases.

[0236] Further, the heat resistance (e.g., heat deformation temperatureand heat decomposition temperature) of the binder in the light-to-heatconverting layer is preferably higher than the heat resistance of thematerials used in other layers provided on the light-to-heat convertinglayer.

[0237] Specifically, acrylate resins, e.g., polymethyl methacrylate,vinyl resins, e.g., polycarbonate, polystyrene, vinyl chloride/vinylacetate copolymer and polyvinyl alcohol, polyvinyl butyral, polyester,polyvinyl chloride, polyamide, polyimide, polyether imide, polysulfone,polyether sulfone, aramid, polyurethane, epoxy resin and urea/melamineresin are exemplified as the binder resins for use in the light-to-heatconverting layer. Of these resins, polyimide resin is preferred.

[0238] Polyimide resins represented by the following formulae (I) to(VII) are soluble in an organic solvent and the productivity of the heattransfer sheet is improved when they are used. Further, these polymideresins are preferred in view of capable of improving the stability ofviscosity, long term storage stability and moisture resistance of thecoating solution for the light-to-heat converting layer.

[0239] In formulae (I) and (II), Ar¹ represents an aromatic grouprepresented by the following formula (1), (2) or (3), and n representsan integer of from 10 to 100.

[0240] In formulae (III) and (IV), Ar² represents an aromatic grouprepresented by the following formula (4), (5), (6) or (7), and nrepresents an integer of from 10 to 100.

[0241] In formulae (V), (VI) and (VII), n and m each represents aninteger of from 10 to 100. In formula (VI), the ratio of n/m is from 6/4to 9/1.

[0242] As the criterion whether a resin is soluble in an organic solventor not, when 10 mass parts (i.e., weight parts) or more of the resin isdissolved in 100 mass parts of N-methylpyrrolidone at 25° C., the resincan be preferably used in the light-to-heat converting layer, morepreferably 100 mass parts is dissolved in 100 mass parts ofN-methylpyrrolidone.

[0243] The light-to-heat converting layer may contain a surfactant, athickener, and an antistatic agent, if necessary.

[0244] The light-to-heat converting layer can be provided by dissolvinga light-to-heat converting material and a binder, adding, if necessary,a matting agent and other components thereto to thereby prepare acoating solution, coating the coating solution on a support and drying.As the organic solvents for dissolving polyimide resins, e.g., n-hexane,cyclohexane, diglyme, xylene, toluene, ethyl acetate, tetrahydrofuran,methyl ethyl ketone, acetone, cyclohexanone, 1,4-dioxane, 1,3-dioxane,dimethyl acetate, N-methyl-2-pyrrolidone, dimethyl sulfoxide,dimethylformamide, dimethylacetamide, y-butyrolactone, ethanol andmethanol can be exemplified. Coating and drying can be performedaccording to ordinary coating and drying methods. Drying is generallyperformed at 300° C. or less, preferably 200° C. or less. Whenpolyethylene terephthalate is used as the support, the dryingtemperature is preferably from 80 to 150° C.

[0245] If the amount of the binder in the light-to-heat converting layeris not sufficient, the cohesive strength of the light-to-heat convertinglayer lowers and the light-to-heat converting layer is liable to betransferred together when an image formed is transferred to animage-receiving sheet, which causes color mixing. While when the amountof the polyimide resin is too much, the layer thickness of thelight-to-heat converting layer becomes too large to achieve a definiteabsorptivity, thereby sensitivity is liable to be decreased. The massratio (i.e., the weight ratio) of the solid content of the light-to-heatconverting material to the binder in the light-to-heat converting layeris preferably 1/20 to 2/1, particularly preferably 1/10 to 2/1.

[0246] As described above, when the layer thickness of the light-to-heatconverting layer is thinned, the sensitivity of the heat transfer sheetis increased and so preferred. The layer thickness of the light-to-heatconverting layer is preferably from 0.03 to 1.0 μm, more preferably from0.05 to 0.5 μm. Further, when the light-to-heat converting layer has theoptical density of from 0.80 to 1.26 to the peak wavelength of laserbeam, e.g., a beam having wavelength of 808 nm, the transfer sensitivityof the image-forming layer is improved, more preferably thelight-to-heat converting layer has the optical density of from 0.92 to1.15. When the optical density at peak wavelength of laser beam is lessthan 0.80, irradiated light cannot be sufficiently converted to heat andsometimes transfer sensitivity is reduced. Contrary to this, when itexceeds 1.26, the function of the light-to-heat converting layer isaffected and sometimes fog is generated. In the present invention, theoptical density of the light-to-heat converting layer in the heattransfer sheet means the absorbance of the light-to-heat convertinglayer at peak wavelength of the laser beams to be used when theimage-forming material of the present invention is subjected torecording, and the optical density can be measured with well-knownspectrophotometers. UV-spectrophotometer UV-240 (manufactured byShimadzu Seisakusho Co. Ltd.) was used in the present invention. Thevalue obtained by subtracting the optical density of the support alonefrom the optical density including the support is taken as the aboveoptical density.

[0247] Image-Forming Layer

[0248] An image-forming layer contains at least a pigment which istransferred to an image-receiving sheet and forms an image, in addition,a binder for forming the layer and, if necessary, other components.

[0249] Pigments are broadly classified to organic pigments and inorganicpigments, and they have respectively characteristics such that theformer are particularly excellent in the transparency of the film, andthe latter are excellent in shielding property, thus they may be usedarbitrarily according to purposes. When the heat transfer sheet is usedfor the proofs of printing colors, organic pigments which are coincidentwith yellow, magenta, cyan and black generally used in printing ink ornear to them in hue are preferably used. Further, metallic powder andfluorescent pigments are also used in some cases. The examples of thepigments which are preferably used include azo pigments, phthalocyaninepigments, anthraquinone pigments, dioxazine pigments, quinacridonepigments, isoindolinone pigments and nitro pigments. The pigments foruse in an image-forming layer are listed below by colors, but thepresent invention is not limited thereto.

[0250] 1) Yellow pigment

[0251] Pigment Yellow 12 (C.I. No. 21090)

[0252] Example:

[0253] Permanent Yellow DHG (manufactured by Clariant Japan, K.K.),Lionol Yellow 1212B (manufactured by Toyo Ink Mfg. Co., Ltd.), IrgaliteYellow LCT (manufactured by Ciba Specialty Chemicals), Symuler FastYellow GTF 219 (manufactured by Dai-Nippon Ink & Chemicals, Inc.)

[0254] Pigment Yellow 13 (C.I. No. 21100)

[0255] Example:

[0256] Permanent Yellow GR (manufactured by Clariant Japan, K. K.),Lionol Yellow 1313 (manufactured by Toyo Ink Mfg. Co., Ltd.)

[0257] Pigment Yellow 14 (C.I. No. 21095)

[0258] Example:

[0259] Permanent Yellow G (manufactured by Clariant Japan, K. K.),Lionol Yellow 1401-G (manufactured by Toyo Ink Mfg. Co., Ltd.), SeikaFast Yellow 2270 (manufactured by Dainichi Seika K.K.), Symuler FastYellow 4400 (manufactured by Dai-Nippon Ink & Chemicals, Inc.)

[0260] Pigment Yellow 17 (C.I. No. 21105)

[0261] Example:

[0262] Permanent Yellow GG02 (manufactured by Clariant Japan, K. K.),Symuler Fast Yellow 8GF (manufactured by Dai-Nippon Ink & Chemicals,Inc.)

[0263] Pigment Yellow 155

[0264] Example:

[0265] Graphtol Yellow 3GP (manufactured by Clariant Japan, K. K.)Pigment Yellow 180 (C.I. No. 21290)

[0266] Example:

[0267] NovopermYellow P-HG (manufacturedby Clariant Japan, K.K.), PVFast Yellow HG (manufactured by Clariant Japan, K.K.) Pigment Yellow 139(C.I. No. 56298)

[0268] Example:

[0269] Novoperm Yellow M2R 70 (manufactured by Clariant Japan, K.K.)

[0270] 2) Magenta Pigment

[0271] Pigment Red 57:1 (C.I. No. 15850:1)

[0272] Example:

[0273] Graphtol Rubine L6B (manufactured by Clariant Japan, K. K.),Lionol Red 6B-4290G (manufactured by Toyo Ink Mfg. Co., Ltd.), IrgaliteRubine 4BL (manufactured by Ciba Specialty Chemicals), Symuler BrilliantCarmine 6B-229 (manufactured by Dai-Nippon Ink & Chemicals, Inc.)Pigment Red 122 (C.I. No. 73915)

[0274] Example:

[0275] Hosterperm Pink E (manufactured by Clariant Japan, K.K.),Lionogen Magenta 5790 (manufactured by Toyo Ink Mfg. Co., Ltd.),FastogenSuper Magenta RH (manufactured by Dai-Nippon Ink & Chemicals, Inc.)

[0276] Pigment Red 53:1 (C.I. No. 15585:1)

[0277] Example:

[0278] Permanent Lake Red LCY (manufactured by Clariant Japan, K. K.),Symuler Lake Red C conc (manufactured by Dai -Nippon Ink & Chemicals,Inc.)

[0279] Pigment Red 48:1 (C.I. No. 15865:1)

[0280] Example:

[0281] Lionol Red 2B-3300 (manufactured by Toyo Ink Mfg. Co., Ltd.),Symuler Red NRY (manufactured by Dai-Nippon Ink & Chemicals, Inc.)

[0282] Pigment Red 48:2 (C.I. No. 15865:2)

[0283] Example:

[0284] Permanent Red W2T (manufactured by Clariant Japan, K. K.), LionolRed LX235 (manufactured by Toyo Ink Mfg. Co., Ltd.), Symuler Red3Ol2(manufactured by Dai-NipponInk & Chemicals, Inc.)

[0285] Pigment Red 48:3 (C.I. No. 15865:3)

[0286] Example:

[0287] Permanent Red 3RL (manufactured by Clariant Japan, K. K.),Symuler Red 2BS (manufactured by Dai-Nippon Ink & Chemicals, Inc.)

[0288] Pigment Red 177 (C.I. No. 65300)

[0289] Example:

[0290] Cromophtal Red A2B (manufactured by Ciba Specialty Chemicals)

[0291] 3) Cyan Pigment

[0292] Pigment Blue 15 (C.I. No. 74160)

[0293] Example:

[0294] Lionol Blue 7027 (manufactured by Toyo Ink Mfg. Co., Ltd.),Fastogen Blue BB (manufactured by Dai-Nippon Ink & Chemicals, Inc.)

[0295] Pigment Blue 15:1 (C.I. No. 74160)

[0296] Example:

[0297] Hosterperm Blue A2R (manufactured by Clariant Japan, K. K.),Fastogen Blue 5050 (manufactured by Dai-Nippon Ink & Chemicals, Inc.)

[0298] Pigment Blue 15:2 (C.I. No. 74160)

[0299] Example:

[0300] Hosterperm Blue AFL (manufactured by Clariant Japan, K. K.),IrgaliteBlueBSP (manufactured by Ciba Specialty Chemicals),FastogenBlueGP (manufactured by Dai-NipponInk & Chemicals, Inc.)

[0301] Pigment Blue 15:3 (C.I. No. 74160)

[0302] Example:

[0303] HosterpermBlueB2G (manufactured by Clariant Japan, K.K.), LionolBlue FG7330 (manufactured by Toyo Ink Mfg. Co., Ltd.), Cromophtal Blue4GNP (manufactured by Ciba Specialty Chemicals), Fastogen Blue FGF(manufactured by Dai-Nippon Ink & Chemicals, Inc.)

[0304] Pigment Blue 15:4 (C.I. No. 74160)

[0305] Example:

[0306] Hosterperm Blue BFL (manufactured by Clariant Japan, K. K.),Cyanine Blue 700-1OFG (manufactured by Toyo Ink Mfg. Co., Ltd.),Irgalite Blue GLNF (manufactured by Ciba Specialty Chemicals), FastogenBlue FGS (manufactured by Dai-Nippon Ink & Chemicals, Inc.)

[0307] Pigment Blue 15:6 (C.I. No. 74160)

[0308] Example:

[0309] Lionol Blue ES (manufactured by Toyo Ink Mfg. Co., Ltd.) PigmentBlue 60 (C.I. No. 69800)

[0310] Example:

[0311] HosterpermBlueRL01 (manufactured by ClariantJapan, K.K.),Lionogen Blue 6501 (manufactured by Toyo Ink Mfg. Co., Ltd.)

[0312] 4) Black Pigment

[0313] Pigment Black 7 (carbon black C.I. No. 77266)

[0314] Example:

[0315] Mitsubishi Carbon Black MA100 (manufactured by MitsubishiChemicals Co., Ltd.), Mitsubishi Carbon Black #5 (manufactured byMitsubishi Chemicals Co., Ltd.), Black Pearls 430 (manufactured by CabotCo.)

[0316] As the pigments which can be used in the present invention,commercially available products can be arbitrarily selected by referringto Ganryo Binran (Pigment Handbook), compiled by Nippon Ganryo GijutsuKyokai, published by Seibundo-Shinko-Sha (1989), and COLOUR INDEX, THESOCIETY OF DYES & COLOURIST, Third Ed. (1987).

[0317] The average particle size of the above pigments is preferablyfrom 0.03 to 1 μm, more preferably from 0.05 to 0.5 μm.

[0318] When the particle size is 0.03 μm or more, the costs fordispersion are not increased and the dispersion solution does not causegelation, while when it is 1 μm or less, since coarse particles are notcontained in pigments, good adhesion of the image-forming layer and theimage-receiving layer can be obtained, further, the transparency of theimage-forming layer can also be improved.

[0319] As the binders for the image-forming layer, amorphous organichigh polymers having a softening point of from 40 to 150° C. arepreferably used. As the amorphous organic high polymers, homopolymersand copolymers of styrene, derivatives thereof, and substitutionproducts thereof, e.g., butyral resin, polyamide resin,polyethyleneimine resin, sulfonamide resin, polyester polyol resin,petroleum resin, styrene, vinyltoluene, a-methylstyrene,2-methylstyrene, chlorostyrene, vinylbenzoic acid, sodiumvinylbenzenesulfonate, and aminostyrene, methacrylic esters andmethacrylic acid, e.g., methyl methacrylate, ethyl methacrylate, butylmethacrylate, and hydroxyethyl methacrylate, acrylic esters and acrylicacid, e.g., methyl acrylate, ethyl acrylate, butyl acrylate, anda-ethylhexyl acrylate, dienes, e.g., butadiene and isoprene,homopolymers of vinyl monomers or copolymers of vinyl monomers withother monomers, e.g., acrylonitrile, vinyl ethers, maleic acid andmaleic esters, maleic anhydride, cinnamic acid, vinyl chloride and vinylacetate can be used. Two or more of these resins may be used as mixture.

[0320] It is preferred for the image-forming layer to contain a pigmentin an amount of from 30 to 70 mass % (i.e., weight %), more preferablyfrom 30 to 50 mass %. It is also preferred for the image-forming layerto contain a resin in an amount of from 30 to 70 mass %, more preferablyfrom 40 to 70 mass %.

[0321] The image-forming layer can contain the following components (1)to (3) as the above-described other components.

[0322] (1) Waxes

[0323] The examples of waxes include mineral waxes, natural waxes andsynthetic waxes. As the examples of the mineral waxes, paraffin wax,microcrystalline wax, ester wax, petroleum wax such as oxide wax, montanwax, ozokerite and ceresin can be exemplified. Paraffin wax is preferredabove all. The paraffin wax is separated from petroleum, and variousproducts are commercially available according to melting points.

[0324] As the examples of the natural waxes, vegetable wax, e.g.,carnauba wax, Japan wax, Quriculy wax and esparto wax, animal wax, e.g.,beeswax, insect wax, shellac wax and spermaceti can be exemplified.

[0325] The synthetic waxes are generally used as a lubricant andgenerally comprises higher fatty acid compounds. As the examples of thesynthetic waxes, the following can be exemplified.

[0326] 1) Fatty Acid-Based Wax

[0327] A straight chain saturated fatty acid represented by thefollowing formula:

CH₃ (CH₂)COOH

[0328] In the formula, n represents an integer of from 6 to 28. As thespecific examples, stearic acid, behenic acid, palmitic acid,12-hydroxystearic acid, and azelaic acid can be exemplified.

[0329] In addition, the metal salts of the above fatty acids (e.g., withK, Ca, Zn and Mg) can be exemplified.

[0330] 2) Fatty Acid Ester-Based Wax

[0331] As the examples of the fatty acid esters, ethyl stearate, laurylstearate, ethyl behenate, hexyl behenate and behenyl myristate can beexemplified.

[0332] 3) Fatty Acid Amide-Based Wax

[0333] As the examples of the fatty acid amides, stearic acid amide andlauric acid amide can be exemplified.

[0334] 4) Aliphatic Alcohol-Based Wax

[0335] A straight chain saturated aliphatic alcohol represented by thefollowing formula:

CH₃ (CH₂)_(n)OH

[0336] In the formula, n represents an integer of from 6 to 28. As thespecific examples, stearyl alcohol can be exemplified.

[0337] Of the above synthetic waxes 1) to 4), higher fatty acid amidessuch as stearic acid amide and lauric acid amide are preferred. Further,these wax compounds can be used alone or in arbitrary combination, asdesired.

[0338] (2) Plasticizers

[0339] As the plasticizers, ester compounds are preferred, andwell-known plasticizers can be exemplified, such as phthalic acidesters, e.g., dibutyl phthalate, di-n-octyl phthalate, di(2-ethylhexyl)phthalate, dinonyl phthalate, dilauryl phthalate, butyllauryl phthalate,and butylbenzyl phthalate, aliphatic dibasic acid esters, e.g., di(2-ethylhexyl) adipate, and di(2-ethylhexyl) sebacate, phosphorictriesters, e.g., tricresyl phosphate and tri(2-ethylhexyl) phosphate,polyol polyesters, e.g., polyethylene glycol ester, and epoxy compounds,e.g.,epoxyfattyacidester. Ofthese,estersofvinylmonomers, in particular,acrylic esters and methacrylic esters are preferred in view of theimprovement of transfer sensitivity, the improvement of transferunevenness, and the big controlling effect of breaking elongation.

[0340] As the acrylic or methacrylic ester compounds, polyethyleneglycol dimethacrylate, 1,2,4-butanetriol trimethacrylate,trimethylolethane triacrylate, pentaerythritol acrylate, pentaerythritoltetraacrylate, dipentaerythritol polyacrylate can be exemplified.

[0341] The above plasticizers may be high polymers, and polyesters arepreferred above all, since the addition effect is large and they hardlydiffuse under storage conditions. As the polyesters, e.g., sebacic acidpolyester and adipic acid polyester are exemplified.

[0342] The additives contained in the image-forming layer are notlimited thereto. The plasticizers may be used alone or in combination oftwo or more.

[0343] When the addition amount of these additives in the image-forminglayer are too much, in some cases, the definition of the transferredimage is deteriorated, the film strength of the image-forming layeritself is reduced, or the unexposed area is transferred to theimage-receiving sheet due to the reduction of the adhesion of thelight-to-heat converting layer and the image-forming layer. From theabove viewpoint, the content of the waxes is preferably from 0.1 to 30mass % (i.e., weight %) of the entire solid content in the image-forminglayer, more preferably from 1 to 20 mass %. The content of theplasticizers is preferably from 0.1 to 20 mass % of the entire solidcontent in the image-forming layer, more preferably from 0.1 to 10 mass%.

[0344] (3) Others

[0345] In addition to the above components, the image-forming layer mayfurther contain a surfactant, inorganic or organic fine particles(metallic powder and silica gel), oils (e.g., linseed oil and mineraloil), a thickener and an antistatic agent. Except for the case ofobtaining a black image, energy necessary for transfer can be reduced bycontaining the materials which absorb the wavelength of the lightsources for use in image recording. As the materials which absorb thewavelength of the light sources, either pigments or dyes may be used,but in the case of obtaining a color image, it is preferred in view ofcolor reproduction to use dyes having less absorption in visible regionand large absorption in the wavelength of light sources and use infraredlight sources such as a semiconductor laser in image recording. As theexamples of infrared absorbing dyes, the compounds disclosed inJP-A-3-103476 can be exemplified.

[0346] The image-forming layer can be provided by dissolving ordispersing the pigment and the binder, to thereby prepare a coatingsolution, coating the coating solution on the light-to-heat convertinglayer (when the following heat-sensitive peeling layer is provided onthe light-to-heat converting layer, on the layer) and drying. As thesolvent for use in the preparation of the coating solution, n-propylalcohol, methyl ethyl ketone, propylene glycol monomethyl ether (MFG),methanol and water can be exemplified. Coating and drying can beperformed according to ordinary coating and drying methods.

[0347] A heat-sensitive peeling layer containing a heat-sensitivematerial which generates gas by the action of the heat generated in thelight-to-heat converting layer or releases adhesive moisture to therebylower the adhesion strength between the light-to-heat converting layerand the image-forming layer can be provided on the light-to-heatconverting layer of the heat transfer sheet. As such heat-sensitivematerials, compounds (polymers or low molecular compounds) whichthemselves are decomposed by heat, or properties of which are changed byheat, and generate gas, and compounds (polymers or low molecularcompounds) which are absorbing, or are being adsorbed with, aconsiderable amount of easily-gasifying gases, such as moisture, can beused. These compounds may be used in combination.

[0348] As the examples of the polymers which themselves are decomposedby heat, or properties of which are changed by heat, and generate gas,self oxidizing polymers, e.g., nitrocellulose, halogen-containingpolymers, e.g., chlorinated polyolefin, chlorinated rubber, poly-rubberchloride, polyvinyl chloride, and polyvinylidene chloride, acryl-basedpolymers, e.g., polyisobutyl methacrylate which is being adsorbed withgasifying compound such as moisture, cellulose esters, e.g., ethylcellulose which is being adsorbed with gasifying compound such asmoisture, and natural high molecular compounds, e.g., gelatin which isbeing adsorbed with gasifying compound such as moisture can beexemplified. As the examples of low molecular compounds which aredecomposed by heat, or properties of which are changed by heat, andgenerate gas, diazo compounds and azide compounds which generate heat,decomposed and generate gas can be exemplified.

[0349] Decomposition and property change by heat of the heat-sensitivematerial as described above preferably occur at 280° C. or less,particularly preferably 230° C. or less.

[0350] When low molecular compounds are used as the heat-sensitivematerial of the heat-sensitive peeling layer, it is preferred to combinethe material with a binder. As the binder, the polymers which themselvesare decomposed by heat, or properties of which are changed by heat, andgenerate gas, can be used, but ordinary binders which do not have suchproperty can also be used. When the heat-sensitive low molecularcompound is used in combination with a binder, the mass ratio (i.e.,weight ratio) of the former to the latter is preferably from 0.02/1 to3/1, more preferably from 0.05/1 to 2/1. It is preferred that theheat-sensitive peeling layer cover the light-to-heat converting layeralmost entirely and the thickness of the heat-sensitive peeling layer isgenerally from 0.03 to 1 μm, and preferably from 0.05 to 0.5 μm.

[0351] When the constitution of the heat transfer sheet comprises asupport having provided thereon a light-to-heat converting layer, aheat-sensitive peeling layer and an image-forming layer in this order,the heat-sensitive peeling layer is decomposed by heat conducted fromthe light-to-heat converting layer, or properties of which are changedby heat, and generates gas. The heat-sensitive peeling layer ispartially lost or cohesive failure is caused in the heat-sensitivepeeling layer due to the decomposition or gas generation, as a resultthe adhesion strength between the light-to-heat converting layer and theimage-forming layer is lowered and, according to the behavior of theheat-sensitive peeling layer, a part of the heat-sensitive peeling layermigrates to the surface of the image finally formed with theimage-forming layer and causes color mixing of the image. Therefore, itis preferred that the heat-sensitive peeling layer is scarcely colored,i.e., the heat-sensitive peeling layer shows high transmittance tovisible rays, so that color mixing does not appear visually on the imageformed, even if such transfer of the heat-sensitive peeling layeroccurs. Specifically, the absorptivity of the heat-sensitive peelinglayer to visible rays is 50% or less, preferably 10% or less.

[0352] Further, instead of providing an independent heat-sensitivepeeling layer, the heat transfer sheet may take the constitution suchthat the light-to-heat converting layer is formed by adding theheat-sensitive material to the coating solution of the light-to-heatconverting layer, and the light-to-heat converting layer doubles as theheat-sensitive peeling layer.

[0353] It is preferred that the coefficient of static friction of theoutermost layer of the heat transfer sheet of the side on which theimage-forming layer is provided is 0.35 or less, preferably 0.20 orless. When the coefficient of static friction of the outermost layer is0.35 or less, the contamination of the roll for carrying the heattransfer sheet can be suppressed and the quality of the image formed canbe improved. The measurement of coefficient of static friction isaccording to the method disclosed in paragraph [0011] ofJP-A-2001-47753.

[0354] It is preferred that the image-forming layer surface has aSmooster value (JAPAN TAPPI No.5) at 23° C., 55% RH of from 0.5 to 50mmHg (=about 0.0665 to 6.65 kPa), and Ra of from 0.05 to 0.4 μm, whichcan reduce a great number of micro voids by which the image-receivinglayer and the image-forming layer cannot be brought into contact witheach other at the contact area, which is preferred in the point oftransfer and image quality. The Ra value can be measured by a surfaceroughness meter (Surfcom, manufactured by Tokyo Seiki Co., Ltd.)according to JIS B0601. It is preferred that the surface hardness of theimage-forming layer is 10 g or more when measured with a sapphireneedle. When the image-forming layer is electrically charged accordingto U.S. test standard 4046 and then grounded, the electrificationpotential 1 second after grounding of the image-forming layer ispreferably from −100 to 100 V. It is preferred that the surfaceresistance of the image-forming layer at 23° C., 55% RH is 10⁹ Ω orless.

[0355] In the next place, the image-receiving sheet which can be used incombination with the heat transfer sheet is described below.

[0356] Image-Receiving Sheet

[0357] Layer Constitution

[0358] The constitution of the image-receiving sheet generally comprisesa support having provided thereon one or more image-receiving layer(s)and, if necessary, any one or two or more layer(s) of a cushioninglayer, a peeling layer and an intermediate layer is(are) providedbetween the support and the image-receiving layer. It is preferred inview of conveyance to provide a backing layer on the surface of thesupport opposite to the side on which the image-receiving layer isprovided.

[0359] Support

[0360] A plastic sheet, a metal sheet, a glass sheet, a resin-coatedpaper, a paper, and ordinary sheet-like substrate materials, e.g.,various composites, are used as the support. As the examples of plasticsheets, a polyethylene terephthalate sheet, apolycarbonate sheet, apolyethylene sheet, a polyvinyl chloride sheet, a polyvinylidenechloride sheet, a polystyrene sheet, a styrene-acrylonitrile sheet, anda polyester sheet can be exemplified. As the examples of papers, anactual printing paper and a coated paper can be used.

[0361] It is preferred for the support to have minute voids in view ofcapable of improving the image quality. Such supports can be produced bymixing a thermoplastic resin and a filler comprising an inorganicpigment and a high polymer incompatible with the above thermoplasticresin to thereby prepare a mixed melt, extruding the mixed melt by amelt extruder to prepare a monolayer or multilayer film, and furthermonoaxially or biaxially stretching the film. In this step, the voidratio is determined by the selection of the resin and the filler, amixing ratio and stretching condition.

[0362] As the thermoplastic resins, a polyolefin resin such aspolypropylene and a polyethylene terephthalate resin are preferred,since they are excellent in crystallizability and orientation propertyand voids can be formed easily. It is preferred to use the polyolefinresin or the polyethylene terephthalate resin as the main component anduse a small amount of other thermoplastic resin arbitrarily incombination. The inorganic pigments for use as the filler preferablyhave an average particle size of from 1 to 20 μm, e.g., calciumcarbonate, clay, diatomaceous earth, titanium oxide, aluminum hydroxideand silica can be used. As the incompatible resins for use as thefiller, when polypropylene is used as the thermoplastic resin, it ispreferred to combine polyethylene terephthalate as the filler. Thesupport having minute voids is disclosed in detail in JP-A-2001-105752.

[0363] The content of the filler, e.g., an inorganic pigment, in thesupport is generally from 2 to 30% or so by volume.

[0364] The thickness of the support in the image-receiving sheet isgenerally from 10 to 400 μm, preferably from 25 to 200 μm. For enhancingthe adhesion with the image-receiving layer (or the cushioning layer) orwith the image-forming layer in the heat transfer sheet, the surface ofthe support in the image-receiving sheet may be subjected to surfacetreatment, e.g., corona discharge treatment and glow dischargetreatment.

[0365] Image-Receiving Layer

[0366] It is preferred to provide one or more image-receiving layer(s)on the support in the image-receiving sheet for transferring and fixingthe image-forming layer on the image-receiving sheet. Theimage-receiving layer is preferably a layer formed with organic polymerbinder as the main component. The binders are preferably thermoplasticresins, such as homopolymers and copolymers of acryl-based monomers,e.g., acrylic acid, methacrylic acid, acrylic ester, and methacrylicester, cellulose-based polymers, e.g., methyl cellulose, ethyl celluloseand cellulose acetate, homomonomers and copolymers of vinyl-basedmonomers, e.g., polystyrene, polyvinyl pyrrolidone, polyvinyl butyral,polyvinyl alcohol andpolyvinyl chloride, condensed polymers, e.g.,polyester and polyamide, and rubber-based polymers, e.g.,butadiene-styrene copolymer. The binder for use in the image-receivinglayer is preferably a polymer having a glass transition temperature (Tg)of 90° C. or lower for obtaining appropriate adhesion with theimage-forming layer. For that purpose, it is possible to added aplasticizer to the image-receiving layer. The binder polymer preferablyhas Tg of 30° C. or more for preventing blocking between sheets. As thebinder polymer of the image-receiving layer, it is particularlypreferred to use the same or analogous binder polymer in theimage-forming layer from the point of improving the adhesion with theimage-forming layer at laser recording and improving sensitivity andimage strength.

[0367] It is preferred that the image-receiving layer surface has aSmooster value (JAPAN TAPPI No.5) at 23° C., 55% RH of from 0.5 to 50mmHg (=about 0.0665 to 6.65 kPa), and Ra of from 0.05 to 0.4 μm, whichcan reduce a great number of micro voids by which the image-receivinglayer and the image-forming layer cannot be brought into contact witheach other at the contact area, which is preferred in the point oftransfer and image quality. The Ra value can be measured by a surfaceroughness meter (Surfcom, manufactured by Tokyo Seiki Co., Ltd.)according to JIS B0601. When the image-receiving layer is electricallycharged according to U.S. test standard 4046 and then grounded, theelectrification potential 1 second after grounding of theimage-receiving layer is preferably from −100 to 100 V. It is preferredthat the surface resistance of the image-receiving layer at 23° C., 55%RH is 10⁹ Ω or less. It is preferred that the coefficient of staticfriction of the surface of the image-receiving layer is 0.2 or less. Itis preferred that the surface energy of the surface of theimage-receiving layer is from 23 to 35 mg/m².

[0368] When the image once formed on the image-receiving layer isre-transferred to the actual printing paper, it is also preferred thatat least one image-receiving layer is formed of a photo-settingmaterial. As the composition of such a photo-setting material,combination comprising a) a photopolymerizable monomer comprising atleast one kind of a polyfunctional vinyl or vinylidene compound whichcan form aphotopolymerbyadditionpolymerization, b) an organicpolymer,and c) a photopolymerization initiator, and, if necessary, additives,e.g., a thermal polymerization inhibitor can be exemplified. As theabove polyfunctional vinyl monomer, unsaturated ester of polyol, inparticular, an acrylic or methacrylic ester (ethylene glycol diacrylate,pentaerythritol tetraacrylate) is used.

[0369] As the organic polymer, the polymers for use for forming theimage-receiving layer can be exemplified. As the photopolymerizationinitiator, an ordinary photo-radical polymerization initiator, e.g.,benzophenone and Michler's ketone, can be used in proportion of from 0.1to 20 mass % (i.e., weight %) in the layer.

[0370] The thickness of the image-receiving layer is generally from 0.3to 7 μm, preferably from 0.7 to 4 μm. When the thickness of theimage-receiving layer is 0.3 μm or more, the film strength can beensured at re-transferring to the actual printing paper. While when itis 4 μm or less, the glossiness of the image after re-transferring tothe actual printing paper can be suppressed, thus the approximation tothe printed matter can be improved.

[0371] The Other Layers

[0372] A cushioning layer may be provided between the support and theimage-receiving layer. When a cushioning layer is provided, it ispossible to increase the adhesion of the image-forming layer and theimage-receiving layer at heat transfer by laser and the image qualitycan be improved. Further, even if foreign matters enter between the heattransfer sheet and the image-receiving sheet during recording, the voidsbetween the image-receiving layer and the image-forming layer arereduced by the deforming action of the cushioning layer, as a result thesize of image defect such as clear spots can be made small. Further,when the image formed by transfer is re-transferred to the actualprinting paper, since the surface of the image-receiving layer isdeformed according to the surface unevenness of the paper, thetransferring property of the image-receiving layer can be improved.Further, by reducing the glossiness of the transferred image, theapproximation to the printed matter can be improved.

[0373] The cushioning layer is formed to be liable to be deformed whenstress is laid on the image-receiving layer, hence for obtaining theabove effect, the cushioning layer preferably comprises materials havinga low modulus of elasticity, materials having elasticity of a rubber, orthermoplastic resins easily softened by heat. The modulus of elasticityof the cushioning layer at room temperature is preferably from 0.5 MPato 1.0 GPa, more preferably from 1 MPa to 0.5 GPa, and particularlypreferably from 10 to 100 MPa. For burying foreign matters such as dust,the penetration according to JIS K2530 (25° C., 100 g, 5 seconds) ispreferably 10 or more. The cushioning layer has a glass transitiontemperature of 80° C. or less, preferably 25° C. or less, and asoftening point of preferably from 50 to 200° C. It is also preferred toadd a plasticizer to the binder for controlling these physicalproperties, e.g., Tg.

[0374] As the specific materials for use as the binder of the cushioninglayer, besides rubbers, e.g., urethane rubber, butadiene rubber, nitrilerubber, acryl rubber and natural rubber, polyethylene, polypropylene,polyester, styrene-butadiene copolymer, ethylene-vinyl acetatecopolymer, ethylene-acryl copolymer, vinyl chloride-vinyl acetatecopolymer, vinylidene chloride resin, vinyl chloride resin containing aplasticizer, polyamide resin and phenol resin can be exemplified.

[0375] The thickness of the cushioning layer varies according to theresins used and other conditions, but is generally from 3 to 100 μm,preferably from 10 to 52 μm.

[0376] It is necessary that the image-receiving layer and the cushioninglayer are adhered to each other until the stage of laser recording, butit is preferred that they are designed to be peelable for transferringan image to the actual printing paper. For easy peeling, it is alsopreferred to provide a peeling layer having a thickness of from 0.1 to 2μm or so between the cushioning layer and the image-receiving layer.When the thickness of the peeling layer is too thick, the properties ofthe cushioning layer are difficult to be exhibited, thus it is necessaryto adjust the thickness by the kind of the peeling layer.

[0377] The specific examples of the binders of the peeling layer includethermo-setting resins having Tg of 65° C. or more, e.g., polyolefin,polyester, polyvinyl acetal, polyvinyl formal, polyparabanic acid,methyl polymethacrylate, polycarbonate, ethyl cellulose, nitrocellulose,methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose,polyvinyl alcohol, polyvinyl chloride, urethane resin, fluorine resin,styrenes, e.g., polystyrene and acrylonitrile styrene, crosslinkedproducts of these resins, polyamide, polyimide, polyether imide,polysulfone, polyether sulfone, aramid, and hardened products of theseresins. As the hardening agent, generally used hardening agents, e.g.,isocyanate and melamine, can be used.

[0378] When the binders of the peeling layer is selected taking theabove physical properties into consideration, polycarbonate, acetal andethyl cellulose are preferred in view of the storage stability, andfurther, when acrylic resins are added to the image-receiving layer,peeling property at re-transferring of the image after laser heattransfer becomes good and preferred.

[0379] Further, a layer whose adhesion with the image-receiving layerextremely lowers by cooling can be used as the peeling layer.Specifically, layers containing waxes, heat fusion compounds such asbinder, and thermoplastic resins as the main component can be used assuch a layer.

[0380] The examples of the heat fusion compounds are disclosed inJP-A-63-193886. In particular, micro crystalline wax, paraffin wax, andcarnauba wax are preferably used. As the thermoplastic resins,ethylene-based copolymers, e.g., ethylene-vinyl acetate resins andcellulose-based resins are preferably used.

[0381] As the additives, higher fatty acid, higher alcohol, higher fattyacid ester, amides, and higher amine can be added to the peeling layer,according to necessity.

[0382] As another constitution of the peeling layer, there is a layerwhich has peeling property by causing cohesive failure due to fusion ormelting by heating. It is preferred to add a supercooling substance tosuch a peeling layer.

[0383] As the supercooling substance, poly-e-caprolactone,polyoxyethylene, benzotriazole, tribenzylamine and vanillin can beexemplified.

[0384] Still another constitution of the peeling layer, a compound toreduce the adhesion with the image-receiving layer is added. As suchcompounds, silicone-based resins, e.g., silicone oil; Teflon,fluorine-based resins, e.g., fluorine-containing acrylic resin;polysiloxane resins; acetal-based resins, e.g., polyvinyl butyral,polyvinyl acetal and polyvinyl formal; solid waxes, e.g., polyethylenewax and amide wax; and fluorine-based and phosphoric ester-basedsurfactants can be exemplified.

[0385] The peeling layer can be prepared by dissolving the abovematerials in a solvent or dispersing the above materials in a latexstate, and coating on the cushioning layer by a blade coater, a rollcoater, a bar coater, a curtain coater, or gravure coater, or extrusionlamination by hot melt. As another method, the solution or dispersionobtained by dissolving the above materials in a solvent or dispersingthe above materials in a latex state is coated on a temporary base bythe above coating method, the temporary base is adhered with thecushioning layer, and then the temporary base is peeled.

[0386] In the image-receiving sheet to be combined with the heattransfer sheet, the image-receiving layer may double as the cushioninglayer, and in that case, the image-receiving sheet may take theconstitution such as support/cushioning image-receiving layer, orsupport/undercoat layer/cushioning image-receiving layer. In this case,it is also preferred that cushioning image-receiving layer has peelingproperty so as to be able to re-transfer to the actual printing paper.In this case, the image after being re-transferred to the actualprinting paper becomes a glossy image.

[0387] The thickness of the cushioning image-receiving layer is from 5to 100 μm, preferably from 10 to 40 μm.

[0388] To provide a backing layer on the side of the support of theimage-receiving sheet opposite to the side on which the image-receivinglayer is provided is preferred for improving the traveling property ofthe image-receiving sheet. When a surfactant, an antistatic agent, e.g.,fine particles of tin oxide, and a matting agent, e.g., silicon oxideand PMMA particles, are added to the backing layer, the travelingproperty in the recording unit is improved.

[0389] These additives can be added not only to the backing layer butalso to the image-receiving layer and other layers, if necessary. Thekinds of the additives cannot be prescribed unconditionally according topurposes, but an antistatic agent can be added by selecting arbitrarilyfrom among various surfactants and electrically conductive agents sothat the surface resistance of the layer at 23° C., 50% RH becomespreferably 10¹² Ω or less, more preferably 10⁹ Ω or less.

[0390] As the binder for use in the backing layer, widely used polymerscan be used, e.g., gelatin, polyvinyl alcohol, methyl cellulose,nitrocellulose, acetyl cellulose, aromatic polyamide resin, siliconeresin, epoxy resin, alkyd resin, phenol resin, melamine resin, fluorineresin, polyimide resin, urethane resin, acryl resin, urethane-modifiedsilicone resin, polyethylene resin, polypropylene resin, polyesterresin, Teflon resin, polyvinyl butyral resin, vinyl chloride-basedresin, polyvinyl acetate, polycarbonate, organic boron compounds,aromatic esters, polyurethane fluoride, and polyether sulfone can beused.

[0391] When crosslinkable water-soluble binder is used as the binder ofthe backing layer and crosslinked, dropout prevention of a matting agentand scratch resistance of the backing layer are improved, further it iseffective for blocking during storage.

[0392] The crosslinking means can be selected with no limitation fromheat, actinic rays and pressure, according to the characteristics of thecrosslinking agent to be used, and these may be used alone or incombination. For providing an adhering property to the support, anarbitrary adhesion layer may be provided on the same side of the supporton which the backing layer is provided.

[0393] The backing layer is preferably provided in an amount of about0.5 to 5 g/m². When the amount is less than 0.5 g/m², coating propertyis unstable, and in heat transfer of thin image-forming layer, thedropout of the recorded image and unevenness are liable to occur.

[0394] It is preferred to add an antistatic agent to the backing layerfor the purpose of preventing adhesion of foreign matters due to thefriction with a carrier roller. As the antistatic agent, a cationicsurfactant, an anionic surfactant, a nonionic surfactant, a highmolecular antistatic agent, electrically conductive fine particles, inaddition, the compounds described in 11290 no Kagaku Shohin (11290Chemical Commercial Products), pp. 875 and 876, Kagaku Kogyo Nippo-Shacan be widely used.

[0395] As antistatic agents which can be used in the backing layer incombination, of the above compounds, metallic oxide, e.g., carbon black,zinc oxide, titanium oxide and tin oxide, and electrically conductivefine particles, e.g., organic semiconductors, are preferably used. Inparticular, when electrically conductive fine particles are used, thedissociation of the antistatic agent from the backing layer can beprevented, and stable antistatic effect can be obtained irrespective ofthe surroundings.

[0396] It is possible to add a mold-releasing agent, e.g., variousactivators, silicone oil, and fluorine resins, to the backing layer forproviding a coating property and a mold-releasing property.

[0397] When the softening point of the cushioning layer and theimage-receiving layer measured by TMA (Thermomechanical Analysis) is 70°C. or lower, it is particularly preferred for the backing layer.

[0398] TMA softening point is obtained by observing the phase of theobject with increasing the temperature of the object of observation atconstant rate and applying a constant load to the object. In the presentinvention, the temperature when the phase of the object begins to changeis defined as TMA, softening point. In the measurement of a softeningpoint by TMA, apparatus such as Thermoflex (manufactured by RigakuDenki-Sha) can be used.

[0399] The heat transfer sheet and the image-receiving sheet can be usedin image forming as the laminate superposing the image-forming layer inthe heat transfer sheet and the image-receiving layer of theimage-receiving sheet.

[0400] The laminate of the heat transfer sheet and the image-receivingsheet can be produced by various methods. For example, the laminate canbe easily obtained by superposing the image-forming layer in the heattransfer sheet and the image-receiving layer in the image-receivingsheet and passing through a pressure and heating roller. The heatingtemperature at this time is 160° C. or less, preferably 130° C. or less.

[0401] The above-described vacuum adhesion method can also be preferablyused for obtaining the laminate. The vacuum adhesion method is a methodof winding the image-receiving sheet around the drum provided withsuction holes for vacuum sucking, and then vacuum-adhering the heattransfer sheet of a little larger size than the image-receiving sheet onthe image-receiving sheet with uniformly blasting air by a squeezeroller. As other method, a method of mechanically sticking theimage-receiving sheet on the metal drum with pulling the image-receivingsheet, and further mechanically sticking the heat transfer sheet thereonwith pulling in the same manner can also be used. Of these methods, thevacuum adhesion method is especially preferred in the point of requiringno temperature control and capable of effecting lamination rapidly anduniformly.

EXAMPLE

[0402] The present invention will be described in detail with referenceto the examples below. In the examples, “parts” means “parts by mass”unless otherwise indicated.

Example 1-1

[0403] Preparation of Heat Transfer Sheet

[0404] Preparation of Heat Transfer Sheet K

[0405] Preparation of First Backing Layer Coating Solution

[0406] The coating solution of the first backing layer was prepared byadding distilled water to 3 parts of a binder (acrylate resin emulsion,Julymer E 410 (20%), manufactured by Nippon JunyakuCo., Ltd.),7. 7partsof electrically conductive metallic oxide fine particles (acicular fineparticles of tin oxide doped with antimony, FS-10 (20%), manufactured byIshihara Sangyo Kaisha Ltd.), 0.2 parts of a crosslinking agent (epoxycompound, Dinacoal Ex614B, manufactured by Nagase Kasei Co., Ltd.), and0.1 parts of a surfactant (polyoxyethylenephenyl ether) to make thetotal 100 parts.

[0407] Formation of First Backing Layer

[0408] One surface (back surface) of a biaxially stretched polyethyleneterephthalate support having a thickness of 75 μm was subjected tocorona discharge treatment. The first backing layer coating solution wascoated on the support in a dry coating thickness of 0.03 μm, dried at180° C. for 30 seconds, thereby the first backing layer was prepared.The Ra of the support of the side on which the image-forming layer sidewas provided was 0.01 μm. The Young's modulus of the support in themachine direction was 450 kg/mm² (=about 4.4 GPa), and the Young'smodulus of the support in the transverse direction was 500 kg/mm²(=about 4.9 GPa). The F-5 value of the support in the machine directionwas 10 kg/mm² (=about 98 MPa), and the F-5 value of the support in thetransverse direction was 13 kg/mm² (=about 127.4 MPa), the heatshrinkage at 100° C. for 30 minutes of the support in the machinedirection was 0.3%, and that in the transverse direction was 0.1%. Thebreaking strength in the machine direction was 20 kg/mm² (=about 196MPa), and that in the transverse direction was 25 kg/mm² (=about 245MPa), and the modulus of elasticity was 400 kg/mm² (=about 3.9 GPa).

[0409] Preparation of Second Backing Layer Coating Solution

[0410] The coating solution of the second backing layer was prepared byadding distilled water to 3 parts of a binder (polyolefin resinemulsion, Chemipearl S-120 (27%), manufactured by Mitsui PetrochemicalIndustries, Ltd.), 2 parts of colloidal silica (Snowtex C (20%),manufactured by Nissan Chemical Industries, Ltd.), 0.3 parts of acrosslinking agent (epoxy resin, Denacol EX-614B, manufactured by NagaseKasei Co., Ltd.), and 0.1 parts of sodium polystyrenesulfonate to makethe total 100 parts.

[0411] Formation of Second Backing Layer

[0412] The second backing layer coating solution was coated on the firstbacking layer in a dry coating thickness of 0.03 μm, dried at 170° C.for 30 seconds, thereby the second backing layer was prepared.

[0413] Preparation of Dispersion of Matting Agent

[0414] Ten parts of spherical silica fine particles having an averageparticle size of 1.5 μm (Seahostar-KE-P150, manufactured by NipponShokubai Co., Ltd.), 2 parts of dispersion polymer (acrylate-styrenecopolymer, Joncryl 611, manufactured by Johnson Polymer Co., Ltd.), 16parts of methyl ethyl ketone, and 64 parts of N-methylpyrrolidone weremixed, this mixture and 30 parts of glass beads having a diameter of 2mm were put in a reaction vessel made of polyethylene having a capacityof 200 ml, and dispersed with a paint shaker (manufactured by Toyo SeikiCo., Ltd.) for 2 hours and silica fine particle dispersion was obtained.

[0415] Preparation of Light-to-Heat Converting Layer Coating Solution

[0416] Methyl ethyl ketone (20 parts), 73 parts of N-methylpyrrolidone,0.4 parts of a binder (a 20% solution of polyimide resin, 8 parts ofRika Coat SN-20F manufactured by Shin Nihon Rika Co., Ltd., an infraredabsorbing dye, NK-2014 manufactured by Nippon Kanko Shikiso Co., Ltd.),and a surfactant (Megafac F-177, manufactured by Dai-Nippon Ink &Chemicals, Inc.) were mixed to dissolve the binder and the infraredabsorbing dye, and 0.7 parts of the above dispersion of the mattingagent was added to the mixture, thereby a light-to-heat converting layercoating solution was prepared.

[0417] Formation of Light-to-Heat Converting Layer

[0418] The above-prepared light-to-heat converting layer coatingsolution was coated with a wire bar on the surface of the support (onthe side opposite to the side on which the first and second backinglayers were coated), dried at 120° C. for 3 minutes, thereby alight-to-heat converting layer was formed. The absorbance of thelight-to-heat converting layer at wavelength of 808 nm was 1.09, and thelayer thickness of the light-to-heat converting layer measured by ascanning electron microscope was 0.35 μm.

[0419] Formation of Image-Forming Layer

[0420] Preparation of Black Image-Forming Layer Coating Solution

[0421] Each of the following components was put in a kneading mill, andpre-treatment of dispersion was performed with adding a small amount ofsolvent and applying a shear force. A solvent was further added to thedispersion so as to reach the following composition, dispersion wasperformed for 2 hours in a sand mill, thereby the mother solution (i.e.,the tank solution) of a pigment dispersion was obtained. Composition ofblack pigment dispersion mother solution Composition 1 Polyvinyl butyral12.6 parts (Eslec B BL-SH, manufactured by Sekisui Chemical Industries,Ltd.) Pigment Black 7 (carbon black,  4.5 parts C.I. No. 77266,Mitsubishi Carbon Black #5, manufactured by Mitsubishi Chemicals Co.Ltd., PVC blackness: 1) Dispersion assistant  0.8 parts (SolspersS-20000, manufactured by ICI) n-Propyl alcohol 79.4 parts Composition 2Polyvinyl butyral 12.6 parts (Eslec B BL-SH, manufactured by SekisuiChemical Industries, Ltd.) Pigment Black 7 (carbon black, 10.5 partsC.I. No. 77266, Mitsubishi Carbon Black MA100, manufactured byMitsubishi Chemicals Co., Ltd., PVC blackness: 10) Dispersion aid  0.8parts (Solspers S-20000, manufactured by ICI) n-Propyl alcohol 79.4parts

[0422] The following components were mixed with stirring by a stirrer toprepare a black image-forming layer coating solution. Composition ofblack image-forming layer coating solution Above black pigmentdispersion mother 185.7 parts solution (composition 1/composition 2:70/30 (parts)) Polyvinyl butyral  11.9 parts (Eslec B BL-SH,manufactured by Sekisui Chemical Industries, Ltd.) Wax-based compoundStearic acid amide (Newtron 2,  1.7 parts manufactured by Nippon SeikaCo., Ltd.) Behenic acid amide (Diamid BM,  1.7 parts (manufactured byNippon Kasei Co., Ltd.) Lauric acid amide (Diamid Y,  1.7 parts(manufactured by Nippon Kasei Co., Ltd.) Palmitic acid amide (Diamid KP, 1.7 parts (manufactured by Nippon Kasei. Co., Ltd.) Erucic acid amide(Diamid L-200,  1.7 parts (manufactured by Nippon Kasei Co., Ltd.) Oleicacid amide (Diamid O-200,  1.7 parts (manufactured by Nippon Kasei Co.,Ltd.) Rosin (KE-311,  11.4 parts (manufactured by Arakawa Kagaku Co.,Ltd.) (components: resin acid 80-97%, resin acid components: abieticacid: 30 to 40% neoabietic acid: 10 to 20% dihydroabietic acid: 14%tetrahydroabietic acid: 14%) Surfactant (Megafac F-176PF,  2.1 partssolid content: 20%, manufactured by Dai-Nippon Ink & Chemicals, Inc.)Inorganic pigment (MEK-ST,  7.1 parts 30% methyl ethyl ketone solution,manufactured by Nissan Chemical Industries, Ltd.) n-Propyl alcohol 1,050parts Methyl ethyl ketone   295 parts

[0423] It was found that the particles in the thus-obtained blackimage-forming layer coating solution had an average particle size of0.25 μm, and the ratio of the particles having a particle size of 1 μmor more was 0.5% from the measurement by particle size distributionmeasuring apparatus of laser scattering system.

[0424] Formation of Black Image-Forming Layer on Light-to-HeatConverting Layer

[0425] The above black image-forming layer coating solution was coatedfor 1 minute with a wire bar coater on the surface of the light-to-heatconverting layer, and the coated product was dried in an oven at 100° C.for 2 minutes, thus a black image-forming layer was formed on thelight-to-heat converting layer. By the above procedure, a heat transfersheet (hereinafter referred to as heat transfer sheet K, similarly, aheat transfer sheet provided with a yellow image-forming layer isreferred to as heat transfer sheet Y, a heat transfer sheet providedwith a magenta image-forming layer is referred to as heat transfer sheetM, and a heat transfer sheet provided with a cyan image-forming layer isreferred to as heat transfer sheet C) comprising a support havingthereon a light-to-heat converting layer and a black image-forming layerin this order was prepared.

[0426] The transmitted optical density of the black image-forming layerof the thus-obtained heat transfer sheet K was 0.91 measured by Macbethdensitometer TD-904 (W filter), and the layer thickness of the blackimage-forming layer measured was 0.60 μm on average.

[0427] The obtained image-forming layer had the following physicalproperties.

[0428] The surface hardness of the image-forming layer with a sapphireneedle having a diameter of 0.5 mm is preferably 100 g or more,specifically 200 g or more.

[0429] The Smooster value of the surface at 23° C., 55% RH is preferablyfrom 0.5 to 50 mmHg (=about 0.0665 to 6.65 kPa), and specifically 9.3mmHg (=about 1.24 kPa).

[0430] The coefficient of static friction of the surface is preferably0.2 or less, and specifically 0.08.

[0431] The surface energy is 29 mJ/m², contact angle with water is94.8°. The reflection optical density is 1.82, the layer thickness is0.60 μm, and OD/layer thickness (μunit) is 3.03.

[0432] The deformation rate of the light-to-heat converting layer was168% when recorded at linear velocity of 1 m/sec or more with laserbeams having light intensity at exposure surface of 1,000 W/mm² or more.

[0433] Preparation of Heat Transfer Sheet Y

[0434] Heat transfer sheet Y was prepared in the same manner as in thepreparation of heat transfer sheet K, except that the yellowimage-forming layer coating solution having the following compositionwas used in place of the black image-forming layer coating solution. Thelayer thickness of the image-forming layer of the obtained heat transfersheet Y was 0.42 μm. Composition of yellow dispersion mother solutionComposition of yellow pigment 1 Polyvinyl butyral  7.1 parts (Eslec BBL-SH, manufactured by Sekisui Chemical Industries, Ltd.) Pigment Yellow(pigment yellow 180, 12.9 parts C.I. No. 21290) (Novoperm Yellow P-HG,manufactured by Clariant Japan, K. K.) Dispersion assistant  0.6 parts(Solspers S-20000, manufactured by ICI) n-Propyl alcohol 79.4 parts

[0435] Composition of yellow dispersion mother solution Composition ofyellow pigment 2 Polyvinyl butyral  7.1 parts (Eslec B BL-SH,manufactured by Sekisui Chemical Industries, Ltd.) Pigment Yellow 139(carbon black, 12.9 parts C.I. No. 56298) (Novoperm Yellow M2R 70,manufactured by Clariant Japan, K. K.) Dispersion assistant  0.6 parts(Solspers S-20000, manufactured by ICI) n-Propyl alcohol 79.4 parts

[0436] Composition of yellow image-forming layer coating solution Aboveyellow pigment dispersion mother  126 parts solution (yellow pigmentcomposition 1/ yellow pigment composition 2: 95/5 (parts)) Polyvinylbutyral  4.6 parts (Eslec B BL-SH, manufactured by Sekisui ChemicalIndustries, Ltd.) Wax-based compound Stearic acid amide (Newtron 2,  0.7parts manufactured by Nippon Seika Co., Ltd.) Behenic acid amide (DiamidBM,  0.7 parts (manufactured by Nippon Kasei Co., Ltd.) Lauric acidamide (Diamid Y,  0.7 parts (manufactured by Nippon Kasei Co., Ltd.)Palmitic acid amide (Diamid KP,  0.7 parts (manufactured by Nippon KaseiCo., Ltd.) Erucic acid amide (Diamid L-200,  0.7 parts (manufactured byNippon Kasei Co., Ltd.) Oleic acid amide (Diamid O-200,  0.7 parts(manufactured by Nippon Kasei Co., Ltd.) Nonionic surfactant  0.4 parts(Chemistat 1100, manufactured by Sanyo Chemical Industries, Co., Ltd.)Rosin (KE-311,  2.4 parts (manufactured by Arakawa Kagaku Co., Ltd.)Surfactant (Megafac F-176PF,  0.8 parts solid content: 20%, manufacturedby Dai-Nippon Ink & Chemicals, Inc.) n-Propyl alcohol  793 parts Methylethyl ketone  198 parts

[0437] The obtained image-forming layer had the following physicalproperties.

[0438] The surface hardness of the image-forming layer with a sapphireneedle having a diameter of 0.5 mm is preferably 100 g or more,specifically 200 g or more.

[0439] The Smooster value of the surface at 23° C., 55% RH is preferablyfrom 0.5 to 50 mmHg (=about 0.0665 to 6.65 kPa), and specifically 2.3mmHg (=about 0.31 kPa).

[0440] The coefficient of static friction of the surface is preferably0.2 or less, and specifically 0.1.

[0441] The surface energy is 24 mJ/m², contact angle with water was108.10. The reflection optical density is 1.01, the layer thickness is0.42 μm, and OD/layer thickness (μunit) is 2.40.

[0442] The deformation rate of the light-to-heat converting layer was150% when recorded at linear velocity of 1 m/sec or more with laserbeams having light strength at exposure surface of 1,000 W/mm² or more.

[0443] Preparation of Heat Transfer Sheet M

[0444] Heat transfer sheet M was prepared in the same manner as in thepreparation of heat transfer sheet K, except that the magentaimage-forming layer coating solution having the following compositionwas used in place of the black image-forming layer coating solution. Thelayer thickness of the image-forming layer of the obtained heat transfersheet M was 0.38 μm. Composition of magenta pigment dispersion mothersolution Composition of magenta pigment 1 Polyvinyl butyral 12.6 parts(Denka Butyral #2000-L, manufactured by Denki Kagaku Kogyo Co., Ltd.,Vicut softening point: 57° C.) Pigment Red (pigment yellow 57:1, 15.0parts C.I. No. 15850:1) (Symuler Brilliant Carmine 6B-229, manufacturedby Dainippon Chemicals and Ink Co., Ltd.) Dispersion aid  0.6 parts(Solspers S-20000, manufactured by ICI) n-Propyl alcohol 80.4 parts

[0445] Composition of magenta pigment dispersion mother solutionComposition of magenta pigment 2 Polyvinyl butyral 12.6 parts (DenkaButyral #2000-L, manufactured by Denki Kagaku Kogyo Co., Ltd., Vicutsoftening point: 57° C.) Pigment Red 57:1 15.0 parts C.I. No. 15850:1)(Lionol Red 6B-4290G, manufactured by Toyo Ink Mfg. Co., Ltd.)Dispersion aid  0.6 parts (Solspers S-20000, manufactured by ICI)n-Propyl alcohol 79.4 parts

[0446] Composition of magenta image-forming layer coating solution Abovemagenta pigment dispersion mother  163 parts solution 1 (magenta pigmentcomposition 1/ magenta pigment composition 2:95/5 (parts)) Polyvinylbutyral  4.0 parts (Denka Butyral #2000-L, manufactured by Denki KagakuKogyo Co., Ltd., Vicut softening point: 57° C.) Wax-based compoundStearic acid amide (Newtron 2,  1.0 parts manufactured by Nippon SeikaCo., Ltd.) Behenic acid amide (Diamid BM,  1.0 parts (manufactured byNippon Kasei Co., Ltd.) Lauric acid amide (Diamid Y,  1.0 parts(manufactured by Nippon Kasei Co., Ltd.) Palmitic acid amide (Diamid KP, 1.0 parts (manufactured by Nippon Kasei Co., Ltd.) Erucic acid amide(Diamid L-200,  1.0 parts (manufactured by Nippon Kasei Co., Ltd.) Oleicacid amide (Diamid O-200,  1.0 parts (manufactured by Nippon Kasei Co.,Ltd.) Nonionic surfactant  0.7 parts (Chemistat 1100, manufactured bySanyo Chemical Industries, Co., Ltd.) Rosin (KE-311,  4.6 parts(manufactured by Arakawa Kagaku Co., Ltd.) Pentaerythritol tetraacrylate 2.5 parts (NK ester A-TMMT, manufactured by Shin-Nakamura Kagaku Co.,Ltd.) Surfactant (Megafac F-176PF,  1.3 parts solid content: 20%,manufactured by Dai-Nippon Ink & Chemicals, Inc.) n-Propyl alcohol  848parts Methyl ethyl ketone  246 parts

[0447] The obtained image-forming layer had the following physicalproperties.

[0448] The surface hardness of the image-forming layer with a sapphireneedle having a diameter of 0.5 mm is preferably 100 g or more,specifically 200 g or more.

[0449] The Smooster value of the surface at 23° C., 55% RH is preferablyfrom 0.5 to 50 mmHg (=about 0.0665 to 6.65 kPa), and specifically 3.5mmHg (=about 0.47 kPa).

[0450] The coefficient of static friction of the surface is preferably0.2 or less, and specifically 0.08.

[0451] The surface energy is 25 mJ/m², contact angle with water is98.8°. The reflection optical density is 1.51, the layer thickness is0.38 μm, and OD/layer thickness (μunit) is 3.97.

[0452] The deformation rate of the light-to-heat converting layer was160% when recorded at linear velocity of 1 m/sec or more with laserbeams having light strength at exposure surface of 1,000 W/mm² or more.

[0453] Preparation of Heat Transfer Sheet C

[0454] Heat transfer sheet C was prepared in the same manner as in thepreparation of heat transfer sheet K, except that the cyan image-forminglayer coating solution having the following composition was used inplace of the black image-forming layer coating solution. The layerthickness of the cyan-forming layer of the obtained heat transfer sheetC was 0.45 μm.

[0455] Composition of Cyan Pigment Dispersion Mother SolutionComposition of cyan pigment 1 Polyvinyl butyral 12.6 parts (Eslec BBL-SH, manufactured by Sekisui Chemical Industries, Ltd.) Pigment Blue(pigment blue 54:7, 15.0 parts C.I. No. 74160) (Cyanine Blue 700-10FG,manufactured by Toyo Ink Mfg. Co., Ltd.)) Dispersion aid  0.8 parts(PW-36, manufactured by Kusumoto Kasei Co., Ltd.) n-Propyl alcohol  110parts

[0456] Composition of Cyan Pigment Dispersion Mother SolutionComposition of cyan pigment 2 Polyvinyl butyral 12.6 parts (Eslec BBL-SH, manufactured by Sekisui Chemical Industries, Ltd.) Pigment Blue15 15.0 parts (C.I. No. 74160, Lionol Blue 7027, manufactured by ToyoInk Mfg. Co., Ltd.) Dispersion aid  0.8 parts (PW-36, manufactured byKusumoto Kasei Co., Ltd.) n-Propyl alcohol  110 parts

[0457] Composition of cyan image-forming layer coating solution Abovecyan pigment dispersion mother 118 parts solution (cyan pigmentcomposition 1/ cyan pigment composition 2:90/10 (parts)) Polyvinylbutyral  5.2 parts (Eslec B BL-SH, manufactured by Sekisui ChemicalIndustries, Ltd.) Inorganic pigment (MEK-ST)  1.3 parts Wax-basedcompound Stearic acid amide (Newtron 2,  1.0 parts manufactured byNippon Seika Co., Ltd.) Behenic acid amide (Diamid BM,  1.0 parts(manufactured by Nippon Kasei Co., Ltd.) Lauric acid amide (Diamid Y, 1.0 parts (manufactured by Nippon Kasei Co., Ltd.) Palmitic acid amide(Diamid KP,  1.0 parts (manufactured by Nippon Kasei Co., Ltd.) Erucicacid amide (Diamid L-200,  1.0 parts (manufactured by Nippon Kasei Co.,Ltd.) Oleic acid amide (Diamid O-200,  1.0 parts (manufactured by NipponKasei Co., Ltd.) Rosin (KE-311,  2.8 parts (manufactured by ArakawaKagaku Co., Ltd.) Pentaerythritol tetraacrylate  1.7 parts (NK esterA-TMMT, manufactured by Shin-Nakamura Kagaku Co., Ltd.) Surfactant(Megafac F-176PF,  1.7 parts solid content: 20%, manufactured byDai-Nippon Ink & Chemicals, Inc.) n-Propyl alcohol 890 parts Methylethyl ketone 247 parts

[0458] The obtained image-forming layer had the following physicalproperties.

[0459] The surface hardness of the image-forming layer with a sapphireneedle having a diameter of 0.5 mm is preferably 100 g or more,specifically 200 g or more.

[0460] The Smooster value of the surface at 23° C., 55% RH is preferablyfrom 0.5 to 50 mmHg (=about 0.0665 to 6.65 kPa), and specifically 7.0mmHg (=about 0.93 kPa).

[0461] The coefficient of static friction of the surface is preferably0.2 or less, and specifically 0.08.

[0462] The surface energy is 25 mJ/m², contact angle with water was98.8°. The reflection optical density is 1.59, the layer thickness is0.45 μm, and OD/layer thickness (μunit) is 3.53.

[0463] The deformation rate of the light-to-heat converting layer was165% when recorded at linear velocity of 1 m/sec or more with laserbeams having light strength at exposure surface of 1,000 W/mm² or more.

[0464] Preparation of Image-Receiving Sheet

[0465] The cushioning layer coating solution and the image-receivinglayer coating solution each having the following composition wereprepared. 1) Cushioning layer coating solution Vinyl chloride-vinylacetate copolymer  20 parts (main binder, MPR-TSL, manufactured byNisshin Kagaku Co., Ltd.) Plasticizer  10 parts (Paraplex G-40,manufactured by CP. HALL. COMPANY) Surfactant (fluorine surfactant, 0.5parts coating assistant, Megafac F-177, manufactured by DainipponChemicals and Ink Co., Ltd.) Antistatic agent (quaternary ammonium salt,0.3 parts SAT-5 Supper (IC), manufactured by Nippon Junyaku Co., Ltd.)Methyl ethyl ketone  60 parts Toluene  10 parts N,N-Dimethylformamide  3 parts

[0466] 2) Image-receiving layer coating solution Polyvinyl butyral   8parts (Eslec B BL-SH, manufactured by Sekisui Chemical Industries, Ltd.)Antistatic agent 0.7 parts Sanstat 2012A, manufactured by Sanyo ChemicalIndustries, Co., Ltd.) Surfactant (Megafac F-177, 0.1 parts manufacturedby Dai-Nippon ink & Chemicals, Inc.) n-Propyl alcohol  20 parts Methanol 20 parts 1-Methoxy-2-propanol  50 parts

[0467] The above-prepared cushioning layer coating solution was coatedon a white PET support (Lumiler #130E58, manufactured by TorayIndustries Inc., thickness: 130 μm) using a narrow-broad coater and thecoated layer was dried, and then the image-receiving layer coatingsolution was coated and dried. The coating amounts were controlled sothat the layer thickness of the cushioning layer after drying becameabout 20 μm and the layer thickness of the image-receiving layer becameabout 2 μm. The white PET support was a void-containing plastic supportof alaminate (total thickness: 130 μm, specific gravity: 0.8) comprisinga void-containing polyethylene terephthalate layer (thickness: 116 μm,void ratio: 20%), and titanium oxide-containing polyethyleneterephthalate layers provided on both sides thereof (thickness: 7 μm,titanium oxide content: 2%). The prepared material was wound in a roll,stored at room temperature for one week, then used in the imagerecording by laser beam as shown below.

[0468] The obtained image-receiving layer had the following physicalproperties.

[0469] The surface roughness Ra is preferably from 0.4 to 0.01 μm, andspecifically 0.02 μm.

[0470] The undulation of the surface of the image-receiving layer ispreferably 2 μm or less, and specifically 1.2 μm.

[0471] The Smooster value of the surface of the image-receiving layer at23° C., 55% RH is preferably from 0.5 to 50 mmHg (=about 0.0665 to 6.65kPa), and specifically 0.8 mmHg (=about 0.11 kPa).

[0472] The coefficient of static friction of the surface of theimage-receiving layer is preferably 0.8 or less, and specifically 0.37.

[0473] The surface energy of the surface of the image-receiving layer is29 mJ/m², contact angle with water is 87.00.

Comparative Example 1-1

[0474] Various kinds of heat transfer sheets were prepared in the samemanner as in Example 1-1 except that dispersion polymer (Joncryl 611)was not used in the preparation of the dispersion of matting agent. Theimage-receiving sheet was the same as in Example 1-1.

Example 1-2

[0475] Various kinds of heat transfer sheets were prepared in the samemanner as in Example 1-1 except that a surfactant (phosphoric acid esterbased surfactant PW-36, manufactured by Kusumoto Kasei Co., Ltd.) wasused in place of Joncryl 611 (manufactured by Johnson Polymer Co.,Ltd.). The image-receiving sheet was the same as in Example 1-1.

Example 1-3

[0476] Various kinds of heat transfer sheets were prepared in the samemanner as in Example 1-1 except that dispersion polymer (SolspersS-20000, manufactured by ICI) was used in place of Joncryl 611(manufactured by Johnson Polymer Co., Ltd.). The image-receiving sheetwas the same as in Example 1 -1 .

[0477] The stability of each light-to-heat converting layer coatingsolution and the property of the image-forming material were evaluatedas follows. The results obtained are shown in Table 1 below.

Example 1-4

[0478] Preparation of Image-Receiving Sheet

[0479] The cushioning layer coating solution having the followingcomposition and the image-receiving layer coating solution wereprepared.

[0480] 1) Cushioning Layer Coating Solution

[0481] The same as in Example 1-1. 2) Image-receiving layer coatingsolution Polyvinyl butyral   8 parts (Eslec B BL-SH, manufactured bySekisui Chemical Industries, Ltd.) Antistatic agent 0.7 parts Sanstat2012A, manufactured by Sanyo Chemical Industries, Co., Ltd.) Surfactant(Megafac F-177, 0.1 parts manufactured by Dainippon Chemicals and InkCo., Ltd.) n-Propyl alcohol  20 parts Methanol  20 parts1-Methoxy-2-propanol  50 parts

[0482] The above components were mixed and polyvinyl butyral wasdissolved, and 0. 8 parts of the dispersion of the matting agent used inExample 1-1 was added thereto, thereby an image-receiving layer coatingsolution was prepared.

[0483] The above-p repared cushioning layer coating solution was coatedwith a wire bar on a white PET support (Lumiler #130E58, manufactured byToray Industries Inc., thickness: 130 μm) using a narrow-broad coaterwith wire bar and the coated layer was dried, and then theimage-receiving layer coating solution was coated and dried. The drycoating amount of the cushioning layer was about 20 μm and that of theimage-receiving layer measured with a scanning electron microscope was2.1 μm. The prepared material was wound in a roll, stored at roomtemperature for one week, then used in the image recording by laser beamas shown below.

[0484] The obtained image-receiving layer had the following physicalproperties.

[0485] The surface roughness Ra is 0.3 μm, the undulation of the surfaceof the image-receiving layer is 1.1 μm, and the Smooster value of thesurface of the image-receiving layer is 2.7 mmHg (=about 0.36 kPa), andthe coefficient of static friction of the surface of the image-receivinglayer is 0.12.

[0486] The same heat transfer sheet as in Comparative Example 1-1 wasused.

Comparative Example 1-2

[0487] An image-receiving sheet was prepared in the same manner as inExample 1-4 except that dispersion polymer (Joncryl 611) was not used inthe preparation of the dispersion of the matting agent.

[0488] The same heat transfer sheet as in Comparative Example 1-1 wasused.

[0489] Evaluation of Stability of Coating Solution

[0490] With respect to the light-to-heat-converting layer coatingsolutions in Examples 1-1 to 1-3 and Comparative Example 1-1, or theimage-receiving layer coating solutions in Examples 1-1 to 1-4 andComparative Example 1-2, each solution was coated immediately afterpreparation and after being allowed to stand at 25° C. for 2 hours toprepare a light-to-heat-converting layer or an image-receiving layer.The state of cohesion of the matting agent in the coated layer wasobserved with an optical microscope. The results of observation wereclassified into four ranks. Those which are classified into Ranks A andB are practicable.

[0491] Rank A: Almost all the particles are dispersed disjointedly oneby one.

[0492] Rank B: A part of the particles are dispersed cohesively by twosand threes.

[0493] Rank C: Almost all the particles are dispersed cohesively by twosand threes.

[0494] Rank D: Almost all the particles are dispersed cohesively by twosand threes, and five or more particles cohere partly.

[0495] Performance of Multicolor Image-Forming Material

[0496] Multicolor Image-Forming Material in Example 1-1

[0497] Formation of Transferred Image

[0498] A transferred image to actual paper was obtained by theimage-forming system shown in FIG. 4 according to the image-formingsequence of the system and the transfer method to actual paper of thesystem, and Luxel FINALPROOF 5600 was used as the recording unit.

[0499] The above-prepared image-receiving sheet (56 cm×79 cm) was woundaround the rotary drum having a diameter of 38 cm, provided with vacuumsuction holes having a diameter of 1 mm (a real density of 1 hole in thearea of 3 cm×8 cm) and vacuum-adsorbed. Subsequently, the above heattransfer sheet K (black) cut into a size of 61 cm×84 cm was superposedon the image-receiving sheet so as to deviate uniformly, squeezed by asqueeze roller, and adhered and laminated so that air was sucked bysuction holes. The degree of pressure reduction in the state of suctionholes being covered was −150 mmHg per 1 atm (=about 81.13 kPa). The drumwas rotated and semiconductor laser beams of the wavelength of 808 nmwere condensed from the outside on the surface of the laminate on thedrum so that the laser beams became a spot of a diameter of 7 μm on thesurface of the light-to-heat converting layer, and laser image recording(line image) was performed on the laminate by moving the laser beam at aright angle (subsidiary scanning ) to the rotary direction of the drum(main scanning direction). The condition of irradiation was as follows.The laser beams used in the example was multi-beam two dimensional arraycomprising five rows along the main scanning direction and three rowsalong the subsidiary scanning direction.

[0500] Laser power: 110 mW

[0501] Drum rotation speed: 500 rpm

[0502] Subsidiary scanning pitch: 6.35 μm

[0503] Surrounding temperature condition:

[0504] 18° C. 30%, 23° C. 50%, 26° C. 65%

[0505] The diameter of exposure drum is preferably 360 mm or more,specifically 380 mm was used.

[0506] The size of the image was 515 mm×728 mm, and the definition was2,600 dpi.

[0507] The laminate finished laser recording was detached from the drumand heat transfer sheet K was peeled from the image-receiving sheet byhands. It was confirmed that only the irradiated domain of theimage-forming layer of heat transfer sheet K had been transferred fromheat transfer sheet K to the image-receiving sheet.

[0508] In the same manner as above, the image was transferred to theimage-receiving sheet from each of heat transfer sheet Y, heat transfersheet M and heat transfer sheet C. The transferred images of four colorswere further transferred to a recording paper and a multicolor image wasformed. Even when high energy laser recording was performed underdifferent temperature humidity conditions with laser beams of multi-beamtwo dimensional array, a multicolor image having excellent image qualityand stable transfer density could be formed.

[0509] In the stage of transfer to the actual paper, the heat transferunit having a dynamic friction coefficient against insert-receivingtable of polyethylene terephthalate of from 0.1 to 0.7 and travelingspeed of from 15 to 50 mm/sec was used. The Vickers hardness of the heatroller of the heat transfer unit is preferably from 10 to 100, andspecifically the heat roller having Vickers hardness of 70 was used.

[0510] Every image under three different surroundings of temperaturehumidity conditions was good.

[0511] Further, the clear spots per m² of the multicolor imagetransferred to recording paper was evaluated. The clear spots mean ablank having a diameter of 1 mm or larger when observed visually.

[0512] The multicolor image-forming materials in other Examples andComparative Examples were also evaluated in the same manner as inExample 1-1. The results obtained are shown in Table 1 below. TABLE 1Stability of Coating Solution Stability Stability Immediately afterBeing White Example after Allowed for Blank No. Preparation 24 HoursArea Example 1-1 A A 0/m² Comparative B D 24/m²  Example 1-1 Example 1-2A A 1/m² Example 1-3 A A 2/m² Example 1-4 A A 0/m² Comparative B D 4/m²Example 1-2

Example 2-1

[0513] Preparation of Heat Transfer Sheet K (Black)

[0514] Formation of Backing Layer Preparation of first backing layercoating solution Water dispersion solution of acrylate   2 parts resin(Julymer ET410, solid content: 20 mass % (i.e., weight %), manufacturedby Nippon Junyaku Co., Ltd.) Antistatic agent (water dispersion  7.0parts of tin oxide-antimony oxide, average particle size: 0.1 μm, 17mass %) Polyoxyethylenephenyl ether  0.1 part Melamine compound  0.3parts (Sumitic Resin M-3, manufactured by Sumitomo Chemical IndustryCo., Ltd.) Distilled water to make the total amount  100 parts

[0515] Formation of First Backing Layer

[0516] One surface (back surface) of a biaxially stretched polyethyleneterephthalate support having a thickness of 75 pm was subjected tocorona discharge treatment. The first backing layer coating solution wascoated on the support in a dry coating thickness of 0.03 μm, dried at180° C. for 30 seconds, thereby the first backing layer was prepared.The Young's modulus of the support in the machine direction was 450kg/mm² (=about 4.4 GPa), and the Young's modulus of the support in thetransverse direction was 500 kg/mm² (=about 4.9 GPa). The F-5 value ofthe support in the machine direction was 10 kg/mm² (=about 98 MPa), andthe F-5 value of the support in the transverse direction was 13 kg/mm²(=about 127.4 MPa), the heat shrinkage at 100° C. for 30 minutes of thesupport in the machine direction was 0.3%, and that in the transversedirection was 0.1%. The breaking strength was 20 kg/mm² (=about 196 MPa)in the machine direction, and that in the transverse direction was 25kg/mm² (=about245 MPa), and the modulus of elasticity was 400 kg/mm²(=about 3.9 GPa). Preparation of second backing layer coating solutionPolyolefin (Chemipearl S-120,  3.0 parts 27 mass %, manufactured byMitsui Petrochemical Industries, Ltd.) Antistatic agent (waterdispersion  2.0 parts of tin oxide-antimony oxide, average particlesize: 0.1 μm, 17 mass %) Colloidal silica  2.0 parts (Snowtex C, 20 mass%, manufactured by Nissan Chemical Industries, Ltd.) Epoxy resin(Denacol EX-614B,  0.3 parts manufactured by Nagase Kasei Co., Ltd.)Distilled water to make the total amount  100 parts

[0517] Formation of Second Backing Layer

[0518] The second backing layer coating solution was coated on the firstbacking layer in dry coating thickness of 0.03 μm, dried at 170° C. for30 seconds, thereby the second backing layer was prepared.

[0519] Formation of Light-to-Heat Converting Layer

[0520] Preparation of Light-to-Heat Converting Layer Coating Solution

[0521] The following components were mixed with stirring by a stirrerand the light-to-heat converting layer coating solution was prepared.Composition of light-to-heat converting layer coating solution Infraredabsorbing dye (NK-2014,  7.6 parts manufactured by Nippon Kanko ShikisoCo., Ltd., cyanine dye having the following composition)

Polyimide resin represented by the 29.3 parts following formula (RikaCoat SN-20F, manufactured by Shin Nihon Rika K. K., heat decompositiontemperature: 510° C.)

[0522] In the formula, R₁ represents SO₂, R₂ represents the followingformula:

or

Exson naphtha 5.8 parts N-Methylpyrrolidone (NMP) 1,500 parts Methylethyl ketone 360 parts Surfactant (Megafac F-176PF, 0.5 partsmanufactured by Dainippon Chemicals and Ink Co., Ltd., fluorinesurfactant) Dispersion of matting agent 14.1 parts having the followingcomposition

[0523] Preparation of Dispersion of Matting Agent

[0524] Ten parts of spherical silica fine particles having an averageparticle size of 1.5 μm (Seahoster-KE-P150, manufactured by NipponShokubai Co., Ltd.), 2 parts of dispersion polymer (acrylate-styrenecopolymer, Joncryl 611, manufactured by Johnson Polymer Co., Ltd.), 16parts of methyl ethyl ketone, and 64 parts of N-methylpyrrolidone weremixed, this mixture and 30 parts of glass beads having a diameter of 2mm were put in a reaction vessel made of polyethylene having a capacityof 200 ml, and dispersed with a paint shaker (manufactured by Toyo SeikiCo., Ltd.) for 2 hours and silica fine particle dispersion was obtained.

[0525] Formation of Light-to-Heat Converting Layer on Support Surface

[0526] The above light-to-heat converting layer coating solution wascoated with a wire bar coater on one surface of a polyethyleneterephthalate film (support) having a thickness of 75 μm, and the coatedproduct was dried in an oven at 120° C. for 2 minutes, thus alight-to-heat converting layer was formed on the support. The opticaldensity (OD) of the thus-obtained light-to-heat converting layer atwavelength of 808 nmmeasured by UV-spectrophotometer UV-240(manufactured by Shimadzu Seisakusho Co. Ltd.) was 1.03, and the layerthickness measured by a scanning electron microscope was 0.3 μm onaverage.

[0527] Subsequently, the same black image-forming layer as in Example1-1 was formed on the light-to-heat converting layer, thus heat-transfersheet K was prepared.

[0528] In the similar manner, the same yellow, magenta or cyanimage-forming layer as in Example 1-1 was formed on the light-to-heatconverting layer, thus heat-transfer sheet Y, M or C was prepared.

[0529] The same image-receiving sheet as in Example 1-1 was used.

[0530] The transferred image was obtained using the multicolorimage-forming material in Example 2-1 by the same image-forming systemas in Example 1-1.

[0531] That is, the above-prepared image-receiving sheet (56 cm×79 cm)was wound around the rotary drum having a diameter of 38 cm, providedwith vacuum suction holes having a diameter of 1 mm (a real density of 1hole in the area of 3 cm×8 cm) and vacuum-adsorbed. Subsequently, theabove heat transfer sheet K (black) cut into a size of 61 cm×84 cm wassuperposed on the image-receiving sheet so as to deviate uniformly,squeezed by a squeeze roller, and adhered and laminated so that air wassucked by suction holes. The degree of pressure reduction in the stateof suction holes being covered was -150 mmHg per 1 atm(=about 81.13kPa). The drum was rotated and semiconductor laser beams of thewavelength of 808 nm were condensed from the outside on the surface ofthe laminate on the drum so that the laser beams became a spot of adiameter of 7 μm on the surface of the light-to-heat converting layer,and laser image recording (line image) was performed on the laminate bymoving the laser beam at a right angle (subsidiary scanning ) to therotary direction of the drum (main scanning direction). The condition ofirradiation was as follows. The laser beams used in the example wasmulti-beam two dimensional array comprising five rows along the mainscanning direction and three rows along the subsidiary scanningdirection.

[0532] Laser power: 110 mW

[0533] Drum rotation speed: 500 rpm

[0534] Subsidiary scanning pitch: 6.35 μm

[0535] Surrounding temperature condition:

[0536] 18° C. 30%, 23° C. 50%, 26° C. 65%

[0537] The diameter of exposure drum is preferably 360 mm or more,specifically 380 mm was used.

[0538] The size of the image was 515 mm×728 mm, and the definition was2,600 dpi.

[0539] The laminate finished laser recording was detached from the drumand heat transfer sheet K was peeled from the image-receiving sheet byhands. It was confirmed that only the irradiated domain of theimage-forming layer of heat transfer sheet K had been transferred fromheat transfer sheet K to the image-receiving sheet.

[0540] In the same manner as above, the image was transferred to theimage-receiving sheet from each of heat transfer sheet Y. heat transfersheet M and heat transfer sheet C. The transferred images of four colorswere further transferred to a recording paper and a multicolor image wasformed. Even when high energy laser recording was performed underdifferent temperature humidity conditions with laser beams of multi-beamtwo dimensional array, a multicolor image having excellent image qualityand stable transfer density could be formed.

[0541] In the stage of transfer to the actual paper, the heat transferunit having a dynamic friction coefficient against insert-receivingtable of polyethylene terephthalate of from 0.1 to 0.7 and travelingspeed of from 15 to 50 mm/sec was used. The Vickers hardness of the heatroller of the heat transfer unit is preferably from 10 to 100, andspecifically the heat roller having Vickers hardness of 70 was used.

[0542] Every image under three different surroundings of temperaturehumidity conditions was good.

[0543] As the optical density, the reflection optical density of eachcolor of Y, M, C, K of the image transferred to Tokuryo art paper wasmeasured in Y, M, C, K mode with a densitometer X-rite 938 (manufacturedby X-rite Co.).

[0544] Optical density, optical density/image-forming layer thickness(μm) of each color are the same as in Example 1-1 as shown in Table 2below. TABLE 2 Optical Optical Density/Image-Forming Color Density LayerThickness Y 1.01 2.40 M 1.51 3.97 C 1.59 3.53 K 1.82 3.03

[0545] The transferred image formed under 23° C. 50% RH was evaluated asfollows.

[0546] Evaluation of Black Image Quality

[0547] Using heat transfer sheet K, the image quality of the solid partand the line image part of the transferred image obtained under eachtemperature-humidity condition was observed with an optical microscope.The time lag in the solid part was not observed in every surroundingcondition, the line definition of the line image was good, andtransferred black images having less dependency on the surroundingcondition could be obtained. The evaluation was performed visuallyaccording to the following criteria.

[0548] Solid Part

[0549] ∘: Time lag in recording time and transfer failure were notobserved.

[0550] Δ: Time lag in recording time and transfer failure were observedpartially.

[0551] ×: Time lag in recording time and transfer failure were observedall over the surface.

[0552] Line Image Part

[0553] ∘: The edge of the line image part was sharp and good definitionwas shown.

[0554] Δ: The edge of the line image part was jagged and bridgingoccurred partially.

[0555] ×: Bridging occurred entirely.

[0556] Evaluation of Unevenness

[0557] Four color images transferred to a recording paper were visuallyobserved and unevenness was evaluated according to the followingcriteria.

[0558] ∘: Unevenness was not observed at all.

[0559] Δ: Unevenness was observed partially.

[0560] ×: Unevenness was observed on 50% or more of the image area.

[0561] Evaluation of Surface Hardness of Image-Forming Layer

[0562] When the surface of the image-forming layer before imageformation is scratched with a sapphire needle having a diameter of 0.5mm at a speed of 1 cm/sec with varying the load, the value representedby gram unit of the minimum load required for the sapphire needle tobreak the image-forming layer and reach the light-to-heat convertinglayer is taken as the hardness of the image-forming layer. This valueindicates the scratch resistance of the image-forming layer.

[0563] Evaluation of Stability of Coating Solution

[0564] After 50 ml of thoroughly stirred light-to-heat converting layercoating solution was poured into a measuring cylinder having an insidediameter of 20 mm and allowed to stand at 25° C. for 30 minutes, whetherfine particles were precipitated or not at the bottom of the measuringcylinder was evaluated.

[0565] ∘: Precipitation of fine particles was not observed.

[0566] ×: Precipitation of fine particles was observed.

[0567] The results of evaluations are shown in Tables 3 and 4 below.

Example 2-2

[0568] A heat transfer sheet was prepared in the same manner as inExample 2-1 except that the amount of the pigment of each of yellow,magenta, cyan and black image-forming layers was made 0.8 times theamount in Example 2-1. However, the optical density of the image-forminglayer was made the same with that in Example 2-1. The image-receivingsheet in Example 1-1 was used.

Reference Example 2-1

[0569] A heat transfer sheet was prepared in the same manner as inExample 2-1 except that amorphous fine particles having an La value of3.5 were used in place of the spherical silica fine particles in thedispersion of the matting agent for use in the light-to-heat convertinglayer coating solution. The image-receiving sheet in Example 1-1 wasused.

Reference Example 2-2

[0570] A heat transfer sheet was prepared in the same manner as inExample 2-1 except that spherical fine particles having an averageparticle size of 0.05 μm were used in place of the spherical silica fineparticles (an average particle size Lb=1.5 μm) in the dispersion of thematting agent for use in the light-to-heat converting layer coatingsolution. The image-receiving sheet in Example 1-1 was used.

Reference Example 2-3

[0571] A heat transfer sheet was prepared in the same manner as inExample 2-1 except that spherical fine particles having an averageparticle size Lb=5.0 μm were used in place of the spherical silica fineparticles (an average particle size Lb=1.5 μm) in the dispersion of thematting agent for use in the light-to-heat converting layer coatingsolution. The image-receiving sheet in Example 1-1 was used.

Reference Example 2-4

[0572] A heat transfer sheet was prepared in the same manner as inExample 2-1 except that spherical fine particles having L₂₅/L₇₅ value of3.2 and an average particle size Lb=1.5 μm were used in place of thespherical silica fine particles (L₂₅/L₇₅ value of 1.1) in the dispersionof the matting agent for use in the light-to-heat converting layercoating solution. The image-receiving sheet in Example 1-1 was used.

Example 2-5

[0573] A heat transfer sheet was prepared in the same manner as inExample 2-1 except that the amount of the pigment of each of yellow,magenta, cyan and black image-forming layers was made 0.6 times theamount in Example 2-1. However, the optical density of the image-forminglayer was made the same with that in Example 2-1. The image-receivingsheet in Example 1-1 was used.

Example 2-6

[0574] A heat transfer sheet was prepared in the same manner as inExample 2-1 except that the amount of the pigment of each of yellow,magenta, cyan and black image-forming layers was made 0.5 times theamount in Example 2-1. However, the optical density of the image-forminglayer was made the same with that in Example 2-1. The image-receivingsheet in Example 1-1 was used.

[0575] Each of the heat transfer sheet prepared in Example 2-2 andComparative Examples 2-1 to 2-6 was also evaluated in the same manner asin Example 1-1. The results obtained are shown in Tables 3 and 4 below.

[0576] The reference examples are an example for exhibiting the effectdue to using or not using the spherical fine particle. TABLE 3 FineParticles Average Example Particle Grain Size Specific No. Shape Size(μm) Distribution Gravity Crystallizability Example 2-1 spherical 1.51.1 1.2 amorphous Example 2-2 spherical 1.5 1.1 1.2 amorphous Referenceirregular 1.5 1.1 1.2 amorphous Example 2-1 Reference spherical 0.05 1.11.2 amorphous Example 2-2 Reference spherical 5.0 1.1 1.2 amorphousExample 2-3 Reference spherical 1.5 3.2 1.2 amorphous Example 2-4Reference spherical 1.5 1.1 1.2 amorphous Example 2-5 Referencespherical 1.5 1.1 1.2 amorphous Example 2-6 Example OD/Layer Thickness(μm) Contact Angle No. Yellow Magenta Cyan Black Yellow Magenta CyanBlack Example 2-1 2.40 3.97 3.53 3.03 108.1 98.8 98.8 94.8 Example 2-21.68 2.91 2.21 2.25 104.5 95.2 92.8 88.6 Reference 2.40 3.97 3.53 3.03108.1 98.8 98.8 94.8 Example 2-1 Reference 2.40 3.97 3.53 3.03 108.198.8 98.8 94.8 Example 2-2 Reference 2.40 3.97 3.53 3.03 108.1 98.8 98.894.8 Example 2-3 Reference 2.40 3.97 3.53 3.03 108.1 98.8 98.8 94.8Example 2-4 Reference 1.11 2.01 1.53 1.58 101.2 92.6 93.1 90.5 Example2-5 Reference 0.87 1.61 1.23 1.28 99.8 90.1 89.6 88.4 Example 2-6

[0577] TABLE 4 Results of Evalution Stability Example Image QualityImage Quality Surface of No. of Solid Part of Line Image Part UnevenessHardness Solution Example 2-1 ∘ ∘ ∘ 200 g or more ∘ Example 2-2 ∘ ∘ ∘200 g or more ∘ Reference ∘ ∘ ∘ 84 g ∘ Example 2-1 Reference ∘ ∘ x 200 gor more ∘ Example 2-2 Reference ∘ ∘ ∘ 200 g or more x Example 2-3Reference ∘ ∘ ∘ 200 g or more x Example 2-4 Reference Δ Δ ∘ 200 g ormore ∘ Example 2-5 Reference x X ∘ 200 g or more ∘ Example 2-6

[0578] It can be seen from the results in Table 4 that the samples inthe examples of the present invention satisfy all of the evaluationitems as compared with the samples in the reference examples.

Example 3-1

[0579] A transferred image was formed in the same manner as in Example2-1 except that a styrene/acrylic acid copolymer (Joncryl 682, weightaverage molecular weight: 1,700, acid value: 238, manufactured byJohnson Polymer Co., Ltd.) was used in place of the acryl-based polymerused in the light-to-heat converting layer coating solution used in thepreparation of the heat transfer sheet.

Example 3-2

[0580] A transferred image was formed in the same manner as in Example2-1 except that a styrene/acrylic acid copolymer (Joncryl 690, weightaverage molecular weight: 15,500, acid value: 240, manufactured byJohnson Polymer Co., Ltd.) was used in place of the acryl-based polymerused in the light-to-heat converting layer coating solution used in thepreparation of the heat transfer sheet.

Example 3-3

[0581] A transferred image was formed in the same manner as in Example2-1 except that the dispersion of the matting agent of the light-to-heatconverting layer coating solution was prepared without using theacryl-based polymer Joncryl 611 but Joncryl 611 was added separately inthe preparation of the heat transfer sheet.

Reference Example 3-1

[0582] A transferred image was formed in the same manner as in Example2-1 except that the acryl-based polymer used in the light-to-heatconverting layer coating solution was not used in the preparation of theheat transfer sheet.

[0583] The reference example is an example for exhibiting the effect dueto using or not using the acryl-based polymer.

[0584] The results of evaluation are shown in Table 5 below with theresults of the following evaluation of the sample in Example 2-1. TABLE5 Constitution Glass Weight Evaluation Transition Average Line ExampleAcryl-Based Point Acid Molecular Solid Image b* of Solid No. Polymer (°C.) Value Weight Part Part Image C Example 2-1 Joncryl 611 50 53 8,100 ∘∘ −48.6 Example 3-1 Joncryl 682 56 238 1,700 ∘ ∘ −47.9 Example 3-2Joncryl 690 102 240 15,500 ∘ ∘ −49.1 Example 3-3 Joncryl 611 50 53 8,100∘ ∘ −48.2 was added separately Reference None — — — ∘ M, K....x −44.2Example 3-1 Y, C....Δ

[0585] The evaluation of images obtained in the above examples wascarried out as follows.

[0586] In the evaluation of the image was carried out with the images offour color, but the evaluation in the hue was described by the value ofcyan image in which the largest change of B* is appeared.

[0587] Evaluation of Image Quality

[0588] Using heat transfer sheets K, C, M and Y, the image quality ofthe solidpart and the line image part of the transferred image obtainedunder each temperature-humidity condition was observed with an opticalmicroscope. The time lag in the solid part was not observed in everysurrounding condition with Examples 3-1 to 3-3, and the line definitionwas good, and transferred images having less dependency on thesurrounding condition could be obtained. The evaluation was performedvisually according to the following criteria.

[0589] Solid Part

[0590] ∘: Time lag in recording time and transfer failure were notobserved.

[0591] Δ: Time lag in recording time and transfer failure were observedpartially.

[0592] ×: Time lag in recording time and transfer failure were observedall over the surface.

[0593] Line Image Part

[0594] ∘: The edge of the line image part was sharp and good definitionwas shown.

[0595] Δ: The edge of the line image part was jagged and bridgingoccurred partially.

[0596] ×: Bridging occurred entirely.

EFFECT OF THE INVENTION

[0597] The present inventors are based on the membrane transfertechnique, and as a result for solving novel problems in laser transfertechnique and further improving the image quality, the present inventorshave developed a heat transfer recording system by laser irradiation forDDCP which comprises an image-forming material of B2 size or largerhaving performances of transfer to actual printing paper, reproductionof actual dots and of a pigment type, output driver, and high grade CMSsoftware. Thus, a system capable of sufficiently exhibiting theperformances of the materials of high definition could be realizedaccording to the present invention. Specifically, the present inventioncan provide proof corresponding to CTP system and contract proofsubstituting analog style color proof. By this proof, color reproductionwhich coincides with printed matters and analog style color proofs forobtaining the approval of customers can be realized. The presentinvention can provide DDCP system by using the same pigment materials asused in the printing inks, effecting transfer to actual paper andgenerating no moire. The present invention can also provide a largesized high grade DDCP (A2/B2 or more) capable of transferring to actualpaper, capable of using the same pigment materials as used in theprinting inks, and showing high approximation to printed matters. Thesystem of the present invention is a system adopting laser membranetransfer, using pigment coloring materials and capable of transferringto actual paper by real dot recording. According to the multicolorimage-forming system according to the present invention, even when laserrecording by high energy using multi-beam two dimensional array underdifferent temperature humidity conditions is performed, an image havinggood image quality and stable transfer density can be formed on theimage-receiving sheet.

[0598] The entitle disclosure of each and every foreign patentapplication from which the benefit of foreign priority has been claimedin the present application is incorporated herein by reference, as iffully set forth herein.

[0599] While the invention has been described in detail and withreference to specific examples thereof, it will be apparent to oneskilled in the art that various changes and modifications can be madetherein without departing from the spirit and scope thereof.

What is claimed is:
 1. A multicolor image-forming material whichcomprises an image-receiving sheet comprising a support having thereon acoating layer including at least an image-receiving layer, and aplurality of heat transfer sheets each comprising a support havingcoating layers including at least a light-to-heat converting layer andan image-forming layer, wherein the ratio of the optical density (OD) ofthe image-forming layer in each heat transfer sheet to the layerthickness, OD/layer thickness (μunit), is 1.50 or more, the recordingarea of a multicolor image of the heat transfer sheet is a size of 515mm or more multiplying 728 mm or more, the definition of a transferredimage is 2,400 dpi or more, and the coating layer in the image-receivingsheet and/or the coating layers in each heat transfer sheet has at leastone layer containing a dispersant and a matting agent having an averageparticle size of from 0.05 to 50 μm.
 2. The multicolor image-formingmaterial as claimed in claim 1, wherein the dispersant is a surfactantand/or a polymer.
 3. The multicolor image-forming material as claimed inclaim 1 or 2, wherein the average particle size of the matting agent isfrom 0.1 to 30 μm.
 4. A method for manufacturing the multicolorimage-forming material as claimed in claim 1, which comprises the stepsof dispersing the matting agent in a dispersion medium with thedispersant in advance to prepare a coating solution containing thedispersed matting agent, coating and drying the prepared coatingsolution to form the layer containing the matting agent, to therebyobtain the multicolor image-forming material.
 5. The method formanufacturing the multicolor image-forming material as claimed in claim4, wherein the water content in the dispersion medium at dispersing thematting agent is 50% or less.
 6. The multicolor image-forming materialas claimed in claim 1, wherein any coating layer in the heat transfersheet and/or the image-receiving sheet contains spherical fine particleshaving an average particle size of from 0.10 to 3.0 μm and a particlesize distribution (L₂₅/L₇₅) of 2.0 or less.
 7. The multicolorimage-forming material as claimed in claim 6, wherein the spherical fineparticles are amorphous fine particles.
 8. The multicolor image-formingmaterial as claimed in claim 6, wherein the spherical fine particleshave an average particle size of from 1.1 to 3.0 μm.
 9. The multicolorimage-forming material as claimed in claim 6, wherein the spherical fineparticles have a specific gravity of from 1.1 to 3.5 at 25° C.
 10. Themulticolor image-forming material as claimed in claim 6, wherein thespherical fine particles have a specific gravity of from 1.1 to 1.4 at25° C.
 11. The multicolor image-forming material as claimed in claim 1,wherein any coating layer in either the heat transfer sheet or theimage-receiving sheet contains an acryl-based polymer having a glasstransition point of from 10 to 120° C.
 12. The multicolor image-formingmaterial as claimed in claim 11, wherein the light-to-heat convertinglayer in the heat transfer sheet contains an acryl-based polymer havinga glass transition point of from 10 to 120° C.
 13. The multicolorimage-forming material as claimed in claim 11, wherein the acid value ofthe acryl-based polymer is 300 or less.
 14. The multicolor image-formingmaterial as claimed in claim 11, wherein the acryl-based polymer hasstructure containing a styrene derivative moiety in the polymermolecule.
 15. The multicolor image-forming material as claimed in claim1, wherein the definition of a transferred image is 2,600 dpi or more.16. The multicolor image-forming material as claimed in claim 1, whereinthe ratio of the optical density (OD) of the image-forming layer in eachheat transfer sheet to the layer thickness, OD/layer thickness (μmunit), is 1.80 or more.
 17. The multicolor image-forming material asclaimed in claim 1, wherein the recording area of a multicolor image is594 mm multiplying 841 mm or more.
 18. The multicolor image-formingmaterial as claimed in claim 1, wherein the contact angle of theimage-forming layer in each heat transfer sheet and the image-receivinglayer in the image-receiving sheet with water is from 7.0 to 120.00. 19.The multicolor image-forming material as claimed in claim 1, wherein theratio of the optical density (OD) of the image-forming layer in eachheat transfer sheet to the layer thickness, OD/layer thickness (μmunit), is 1.80 or more, and the contact angle of the image-receivingsheet with water is 890 or less.
 20. The multicolor image-formingmaterial as claimed in claim 1, wherein the ratio of the optical density(OD) of the image-forming layer in each heat transfer sheet to the layerthickness, OD/layer thickness (μm unit), is 2.50 or more.
 21. A methodfor forming a multicolor image using the image-receiving sheet asclaimed in claim 1 and four or more heat transfer sheets as claimed inclaim 1 comprising the steps of superposing the image-forming layer ineach heat transfer sheet and the image-receiving layer in theimage-receiving sheet vis-a-vis, and irradiating the heat transfer sheetfrom the support side with laser beams and transferring the area of theimage-forming layer subjected to laser beam irradiation onto theimage-receiving layer in the image-receiving sheet, to thereby effectimage-recording, wherein the image-forming layer in the laser beamirradiation area is transferred to the image-receiving sheet in amembrane state.